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An Y, Guo X, Yan T, Jia Y, Jiao R, Cai X, Deng B, Bao G, Li Y, Yang W, Wang R, Sun W, Xie J. Enhancing the stability and therapeutic potential of the antimicrobial peptide Feleucin-K3 against Multidrug-Resistant a. Baumannii through rational utilization of a D-amino acid substitution strategy. Biochem Pharmacol 2024; 225:116269. [PMID: 38723723 DOI: 10.1016/j.bcp.2024.116269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 05/05/2024] [Accepted: 05/06/2024] [Indexed: 05/12/2024]
Abstract
Antimicrobial peptides (AMPs), which have a low probability of developing resistance, are considered the most promising antimicrobial agents for combating antibiotic resistance. Feleucin-K3 is an amphiphilic cationic AMP that exhibits broad-spectrum antimicrobial activity. In our previous research, the first phenylalanine residue was identified as the critical position affecting its biological activity. Here, a series of Feleucin-K3 analogs containing hydrophobic D-amino acids were developed, leveraging the low sensitivity of proteases to unnatural amino acids and the regulatory effect of hydrophobicity on antimicrobial activity. Among them, K-1dF, which replaced the phenylalanine of Feleucin-K3 with its enantiomer (D-phenylalanine), exhibited potent antimicrobial activity with a therapeutic index of 46.97 and MICs between 4 to 8 μg/ml against both sensitive and multidrug-resistant Acinetobacter baumannii. The introduction of D-phenylalanine increased the salt tolerance and serum stability of Feleucin-K3. Moreover, K-1dF displayed a rapid bactericidal effect, a low propensity to develop resistance, and a synergistic effect when combined with antibiotics. More importantly, it exhibited considerable or superior efficacy to imipenem against pneumonia and skin abscess infection. In brief, the K-1dF obtained by simple and effective modification strategy has emerged as a promising candidate antimicrobial agent for tackling multidrug-resistant Acinetobacter baumannii infections.
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Affiliation(s)
- Yingying An
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China
| | - Xiaomin Guo
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China
| | - Tiantian Yan
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China
| | - Yue Jia
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China
| | - Ruoyan Jiao
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China
| | - Xinyu Cai
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China
| | - Bochuan Deng
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China
| | - Guangjun Bao
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China
| | - Yiping Li
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China
| | - Wenle Yang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China
| | - Rui Wang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China; State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
| | - Wangsheng Sun
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China.
| | - Junqiu Xie
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences & Research Unit of Peptide Science, Chinese Academy of Medical Sciences, 2019RU066, Lanzhou University, Lanzhou 730000, China.
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2
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Yoon Y, Song S. Structural Insights into the Lipopolysaccharide Transport (Lpt) System as a Novel Antibiotic Target. J Microbiol 2024; 62:261-275. [PMID: 38816673 DOI: 10.1007/s12275-024-00137-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 04/15/2024] [Accepted: 04/15/2024] [Indexed: 06/01/2024]
Abstract
Lipopolysaccharide (LPS) is a critical component of the extracellular leaflet within the bacterial outer membrane, forming an effective physical barrier against environmental threats in Gram-negative bacteria. After LPS is synthesized and matured in the bacterial cytoplasm and the inner membrane (IM), LPS is inserted into the outer membrane (OM) through the ATP-driven LPS transport (Lpt) pathway, which is an energy-intensive process. A trans-envelope complex that contains seven Lpt proteins (LptA-LptG) is crucial for extracting LPS from the IM and transporting it across the periplasm to the OM. The last step in LPS transport involves the mediation of the LptDE complex, facilitating the insertion of LPS into the outer leaflet of the OM. As the Lpt system plays an essential role in maintaining the impermeability of the OM via LPS decoration, the interactions between these interconnected subunits, which are meticulously regulated, may be potential targets for the development of new antibiotics to combat multidrug-resistant Gram-negative bacteria. In this review, we aimed to provide an overview of current research concerning the structural interactions within the Lpt system and their implications to clarify the function and regulation of LPS transport in the overall process of OM biogenesis. Additionally, we explored studies on the development of therapeutic inhibitors of LPS transport, the factors that limit success, and future prospects.
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Affiliation(s)
- Yurim Yoon
- Infectious Diseases Therapeutic Research Center, Korea Research Institute of Chemical Technology, Daejeon, 34114, Republic of Korea
| | - Saemee Song
- Infectious Diseases Therapeutic Research Center, Korea Research Institute of Chemical Technology, Daejeon, 34114, Republic of Korea.
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3
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Yang Y, Chen H, Corey RA, Morales V, Quentin Y, Froment C, Caumont-Sarcos A, Albenne C, Burlet-Schiltz O, Ranava D, Stansfeld PJ, Marcoux J, Ieva R. LptM promotes oxidative maturation of the lipopolysaccharide translocon by substrate binding mimicry. Nat Commun 2023; 14:6368. [PMID: 37821449 PMCID: PMC10567701 DOI: 10.1038/s41467-023-42007-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 09/27/2023] [Indexed: 10/13/2023] Open
Abstract
Insertion of lipopolysaccharide (LPS) into the bacterial outer membrane (OM) is mediated by a druggable OM translocon consisting of a β-barrel membrane protein, LptD, and a lipoprotein, LptE. The β-barrel assembly machinery (BAM) assembles LptD together with LptE at the OM. In the enterobacterium Escherichia coli, formation of two native disulfide bonds in LptD controls translocon activation. Here we report the discovery of LptM (formerly YifL), a lipoprotein conserved in Enterobacteriaceae, that assembles together with LptD and LptE at the BAM complex. LptM stabilizes a conformation of LptD that can efficiently acquire native disulfide bonds, whereas its inactivation makes disulfide bond isomerization by DsbC become essential for viability. Our structural prediction and biochemical analyses indicate that LptM binds to sites in both LptD and LptE that are proposed to coordinate LPS insertion into the OM. These results suggest that, by mimicking LPS binding, LptM facilitates oxidative maturation of LptD, thereby activating the LPS translocon.
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Affiliation(s)
- Yiying Yang
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Haoxiang Chen
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Robin A Corey
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences Building, Bristol, BS8 1TD, UK
| | - Violette Morales
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Yves Quentin
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Carine Froment
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31077, France
- Infrastructure Nationale de Protéomique, ProFI, FR 2048, Toulouse, France
| | - Anne Caumont-Sarcos
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Cécile Albenne
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Odile Burlet-Schiltz
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31077, France
- Infrastructure Nationale de Protéomique, ProFI, FR 2048, Toulouse, France
| | - David Ranava
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France
| | - Phillip J Stansfeld
- School of Life Sciences and Department of Chemistry, Gibbet Hill Campus, The University of Warwick, Coventry, CV4 7AL, UK
| | - Julien Marcoux
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31077, France
- Infrastructure Nationale de Protéomique, ProFI, FR 2048, Toulouse, France
| | - Raffaele Ieva
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III - Paul Sabatier (UT3), Toulouse, 31062, France.
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Sabnis A, Edwards AM. Lipopolysaccharide as an antibiotic target. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119507. [PMID: 37268022 DOI: 10.1016/j.bbamcr.2023.119507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 04/18/2023] [Accepted: 05/14/2023] [Indexed: 06/04/2023]
Abstract
Gram-negative bacteria, including Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii are amongst the highest priority drug-resistant pathogens, for which new antibiotics are urgently needed. Whilst antibiotic drug development is inherently challenging, this is particularly true for Gram-negative bacteria due to the presence of the outer membrane, a highly selective permeability barrier that prevents the ingress of several classes of antibiotic. This selectivity is largely due to an outer leaflet composed of the glycolipid lipopolysaccharide (LPS), which is essential for the viability of almost all Gram-negative bacteria. This essentiality, coupled with the conservation of the synthetic pathway across species and recent breakthroughs in our understanding of transport and membrane homeostasis has made LPS an attractive target for novel antibiotic drug development. Several different targets have been explored and small molecules developed that show promising activity in vitro. However, these endeavours have met limited success in clinical testing and the polymyxins, discovered more than 70 years ago, remain the only LPS-targeting drugs to enter the clinic thus far. In this review, we will discuss efforts to develop therapeutic inhibitors of LPS synthesis and transport and the reasons for limited success, and explore new developments in understanding polymyxin mode of action and the identification of new analogues with reduced toxicity and enhanced activity.
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Affiliation(s)
- Akshay Sabnis
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Rd, London SW7 2AZ, UK
| | - Andrew M Edwards
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Rd, London SW7 2AZ, UK.
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5
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Jensen SJ, Ruhe ZC, Williams AF, Nhan DQ, Garza-Sánchez F, Low DA, Hayes CS. Paradoxical Activation of a Type VI Secretion System Phospholipase Effector by Its Cognate Immunity Protein. J Bacteriol 2023; 205:e0011323. [PMID: 37212679 PMCID: PMC10294671 DOI: 10.1128/jb.00113-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 05/03/2023] [Indexed: 05/23/2023] Open
Abstract
Type VI secretion systems (T6SSs) deliver cytotoxic effector proteins into target bacteria and eukaryotic host cells. Antibacterial effectors are invariably encoded with cognate immunity proteins that protect the producing cell from self-intoxication. Here, we identify transposon insertions that disrupt the tli immunity gene of Enterobacter cloacae and induce autopermeabilization through unopposed activity of the Tle phospholipase effector. This hyperpermeability phenotype is T6SS dependent, indicating that the mutants are intoxicated by Tle delivered from neighboring sibling cells rather than by internally produced phospholipase. Unexpectedly, an in-frame deletion of tli does not induce hyperpermeability because Δtli null mutants fail to deploy active Tle. Instead, the most striking phenotypes are associated with disruption of the tli lipoprotein signal sequence, which prevents immunity protein localization to the periplasm. Immunoblotting reveals that most hyperpermeable mutants still produce Tli, presumably from alternative translation initiation codons downstream of the signal sequence. These observations suggest that cytosolic Tli is required for the activation and/or export of Tle. We show that Tle growth inhibition activity remains Tli dependent when phospholipase delivery into target bacteria is ensured through fusion to the VgrG β-spike protein. Together, these findings indicate that Tli has distinct functions, depending on its subcellular localization. Periplasmic Tli acts as a canonical immunity factor to neutralize incoming effector proteins, while a cytosolic pool of Tli is required to activate the phospholipase domain of Tle prior to T6SS-dependent export. IMPORTANCE Gram-negative bacteria use type VI secretion systems deliver toxic effector proteins directly into neighboring competitors. Secreting cells also produce specific immunity proteins that neutralize effector activities to prevent autointoxication. Here, we show the Tli immunity protein of Enterobacter cloacae has two distinct functions, depending on its subcellular localization. Periplasmic Tli acts as a canonical immunity factor to block Tle lipase effector activity, while cytoplasmic Tli is required to activate the lipase prior to export. These results indicate Tle interacts transiently with its cognate immunity protein to promote effector protein folding and/or packaging into the secretion apparatus.
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Affiliation(s)
- Steven J. Jensen
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Zachary C. Ruhe
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - August F. Williams
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Dinh Q. Nhan
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Fernando Garza-Sánchez
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - David A. Low
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, USA
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Christopher S. Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, USA
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, California, USA
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6
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Jensen SJ, Ruhe ZC, Williams AF, Nhan DQ, Garza-Sánchez F, Low DA, Hayes CS. Paradoxical activation of a type VI secretion system (T6SS) phospholipase effector by its cognate immunity protein. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.28.534661. [PMID: 37034769 PMCID: PMC10081291 DOI: 10.1101/2023.03.28.534661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Type VI secretion systems (T6SS) deliver cytotoxic effector proteins into target bacteria and eukaryotic host cells. Antibacterial effectors are invariably encoded with cognate immunity proteins that protect the producing cell from self-intoxication. Here, we identify transposon insertions that disrupt the tli immunity gene of Enterobacter cloacae and induce auto-permeabilization through unopposed activity of the Tle phospholipase effector. This hyper-permeability phenotype is T6SS-dependent, indicating that the mutants are intoxicated by Tle delivered from neighboring sibling cells rather than by internally produced phospholipase. Unexpectedly, an in-frame deletion of tli does not induce hyper-permeability because Δ tli null mutants fail to deploy active Tle. Instead, the most striking phenotypes are associated with disruption of the tli lipoprotein signal sequence, which prevents immunity protein localization to the periplasm. Immunoblotting reveals that most hyper-permeable mutants still produce Tli, presumably from alternative translation initiation codons downstream of the signal sequence. These observations suggest that cytosolic Tli is required for the activation and/or export of Tle. We show that Tle growth inhibition activity remains Tli-dependent when phospholipase delivery into target bacteria is ensured through fusion to the VgrG β-spike protein. Together, these findings indicate that Tli has distinct functions depending on its subcellular localization. Periplasmic Tli acts as a canonical immunity factor to neutralize incoming effector proteins, while a cytosolic pool of Tli is required to activate the phospholipase domain of Tle prior to T6SS-dependent export.
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7
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Bilsing FL, Anlauf MT, Hachani E, Khosa S, Schmitt L. ABC Transporters in Bacterial Nanomachineries. Int J Mol Sci 2023; 24:ijms24076227. [PMID: 37047196 PMCID: PMC10094684 DOI: 10.3390/ijms24076227] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 03/18/2023] [Accepted: 03/23/2023] [Indexed: 03/29/2023] Open
Abstract
Members of the superfamily of ABC transporters are found in all domains of life. Most of these primary active transporters act as isolated entities and export or import their substrates in an ATP-dependent manner across biological membranes. However, some ABC transporters are also part of larger protein complexes, so-called nanomachineries that catalyze the vectorial transport of their substrates. Here, we will focus on four bacterial examples of such nanomachineries: the Mac system providing drug resistance, the Lpt system catalyzing vectorial LPS transport, the Mla system responsible for phospholipid transport, and the Lol system, which is required for lipoprotein transport to the outer membrane of Gram-negative bacteria. For all four systems, we tried to summarize the existing data and provide a structure-function analysis highlighting the mechanistical aspect of the coupling of ATP hydrolysis to substrate translocation.
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Chemical Profiling, Bioactive Properties, and Anticancer and Antimicrobial Potential of Juglans regia L. Leaves. Molecules 2023; 28:molecules28041989. [PMID: 36838977 PMCID: PMC9966981 DOI: 10.3390/molecules28041989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 02/15/2023] [Accepted: 02/17/2023] [Indexed: 02/22/2023] Open
Abstract
The aim of this study was to assess the biological potential of the polyphenolic fraction isolated from J. regia leaves, collected in the Subcarpathian region (Poland). The phenolic profile was determined using the UPLC-PDA-MS/MS method. Biological activity was determined by evaluating the antioxidant, anticancer, antibacterial, and antifungal effects. Prior to this study, the purified polyphenolic fraction was not been tested in this regard. A total of 40 phenolic compounds (104.28 mg/g dw) were identified, with quercetin 3-O-glucoside and quercetin pentosides dominating. The preparation was characterized by a high ability to chelate iron ions and capture O2•- and OH• radicals (reaching IC50 values of 388.61, 67.78 and 193.29 µg/mL, respectively). As for the anticancer activity, among the six tested cell lines, the preparation reduced the viability of the DLD-1, Caco-2, and MCF-7 lines the most, while in the antibacterial activity, among the seven tested strains, the highest susceptibility has been demonstrated against K. pneumoniae, S. pyogenes, and S. aureus. Depending on the needs, such a preparation can be widely used in the design of functional food and/or the cosmetics industry.
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Sperandeo P, Martorana AM, Zaccaria M, Polissi A. Targeting the LPS export pathway for the development of novel therapeutics. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119406. [PMID: 36473551 DOI: 10.1016/j.bbamcr.2022.119406] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 10/14/2022] [Accepted: 11/01/2022] [Indexed: 12/12/2022]
Abstract
The rapid rise of multi-resistant bacteria is a global health threat. This is especially serious for Gram-negative bacteria in which the impermeable outer membrane (OM) acts as a shield against antibiotics. The development of new drugs with novel modes of actions to combat multi-drug resistant pathogens requires the selection of suitable processes to be targeted. The LPS export pathway is an excellent under exploited target for drug development. Indeed, LPS is the major determinant of the OM permeability barrier, and its biogenetic pathway is conserved in most Gram-negatives. Here we describe efforts to identify inhibitors of the multiprotein Lpt system that transports LPS to the cell surface. Despite none of these molecules has been approved for clinical use, they may represent valuable compounds for optimization. Finally, the recent discovery of a link between inhibition of LPS biogenesis and changes in peptidoglycan structure uncovers additional targets to develop novel therapeutic strategies.
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Affiliation(s)
- Paola Sperandeo
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy
| | - Alessandra M Martorana
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy
| | - Marta Zaccaria
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy
| | - Alessandra Polissi
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy.
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10
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Bowen HG, Kenedy MR, Johnson DK, MacKerell AD, Akins DR. Identification of a novel transport system in Borrelia burgdorferi that links the inner and outer membranes. Pathog Dis 2023; 81:ftad014. [PMID: 37385817 PMCID: PMC10353723 DOI: 10.1093/femspd/ftad014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 06/19/2023] [Accepted: 06/27/2023] [Indexed: 07/01/2023] Open
Abstract
Borrelia burgdorferi, the spirochete that causes Lyme disease, is a diderm organism that is similar to Gram-negative organisms in that it contains both an inner and outer membrane. Unlike typical Gram-negative organisms, however, B. burgdorferi lacks lipopolysaccharide (LPS). Using computational genome analyses and structural modeling, we identified a transport system containing six proteins in B. burgdorferi that are all orthologs to proteins found in the lipopolysaccharide transport (LPT) system that links the inner and outer membranes of Gram-negative organisms and is responsible for placing LPS on the surface of these organisms. While B. burgdorferi does not contain LPS, it does encode over 100 different surface-exposed lipoproteins and several major glycolipids, which like LPS are also highly amphiphilic molecules, though no system to transport these molecules to the borrelial surface is known. Accordingly, experiments supplemented by molecular modeling were undertaken to determine whether the orthologous LPT system identified in B. burgdorferi could transport lipoproteins and/or glycolipids to the borrelial outer membrane. Our combined observations strongly suggest that the LPT transport system does not transport lipoproteins to the surface. Molecular dynamic modeling, however, suggests that the borrelial LPT system could transport borrelial glycolipids to the outer membrane.
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Affiliation(s)
- Hannah G Bowen
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., BMSB 1053 Oklahoma City, OK 73104, United States
| | - Melisha R Kenedy
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., BMSB 1053 Oklahoma City, OK 73104, United States
| | - David K Johnson
- Shenkel Structural Biology Center, Molecular Graphics and Modeling Laboratory and the Computational Biology Core, University of Kansas, 2034 Becker Drive Lawrence, Kansas 66047, United States
| | - Alexander D MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore 20 North Pine Street Baltimore, Maryland 21201, United States
| | - Darrin R Akins
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., BMSB 1053 Oklahoma City, OK 73104, United States
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11
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Giacometti SI, MacRae MR, Dancel-Manning K, Bhabha G, Ekiert DC. Lipid Transport Across Bacterial Membranes. Annu Rev Cell Dev Biol 2022; 38:125-153. [PMID: 35850151 DOI: 10.1146/annurev-cellbio-120420-022914] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The movement of lipids within and between membranes in bacteria is essential for building and maintaining the bacterial cell envelope. Moving lipids to their final destination is often energetically unfavorable and does not readily occur spontaneously. Bacteria have evolved several protein-mediated transport systems that bind specific lipid substrates and catalyze the transport of lipids across membranes and from one membrane to another. Specific protein flippases act in translocating lipids across the plasma membrane, overcoming the obstacle of moving relatively large and chemically diverse lipids between leaflets of the bilayer. Active transporters found in double-membraned bacteria have evolved sophisticated mechanisms to traffic lipids between the two membranes, including assembling to form large, multiprotein complexes that resemble bridges, shuttles, and tunnels, shielding lipids from the hydrophilic environment of the periplasm during transport. In this review, we explore our current understanding of the mechanisms thought to drive bacterial lipid transport.
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Affiliation(s)
- Sabrina I Giacometti
- Department of Cell Biology, New York University School of Medicine, New York, NY, USA; , , ,
| | - Mark R MacRae
- Department of Cell Biology, New York University School of Medicine, New York, NY, USA; , , ,
| | - Kristen Dancel-Manning
- Office of Science and Research, New York University School of Medicine, New York, NY, USA;
| | - Gira Bhabha
- Department of Cell Biology, New York University School of Medicine, New York, NY, USA; , , ,
| | - Damian C Ekiert
- Department of Cell Biology, New York University School of Medicine, New York, NY, USA; , , ,
- Department of Microbiology, New York University School of Medicine, New York, NY, USA
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12
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Wilson A, Ruiz N. The transmembrane α-helix of LptC participates in LPS extraction by the LptB 2 FGC transporter. Mol Microbiol 2022; 118:61-76. [PMID: 35678757 PMCID: PMC9544173 DOI: 10.1111/mmi.14952] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 06/06/2022] [Accepted: 06/07/2022] [Indexed: 11/28/2022]
Abstract
Lipopolysaccharide (LPS) is an essential component of the outer membrane of most Gram‐negative bacteria that provides resistance to various toxic compounds and antibiotics. Newly synthesized LPS is extracted from the inner membrane by the ATP‐binding cassette (ABC) transporter LptB2FGC, which places the glycolipid onto a periplasmic protein bridge that connects to the outer membrane. This ABC transporter is structurally unusual in that it associates with an additional protein, LptC. The periplasmic domain of LptC is part of the transporter's bridge while its transmembrane α‐helix intercalates into the LPS‐binding cavity of the core LptB2FG transporter. LptC’s transmembrane helix affects the in vitro ATPase activity of LptB2FG, but its role in LPS transport in cells remains undefined. Here, we describe two roles of LptC’s transmembrane helix in Escherichia coli. We demonstrate that it is required to maintain proper levels of LptC and participates in coupling the activity of the ATPase LptB to that of its transmembrane partners LptF/LptG prior to loading LPS onto the periplasmic bridge. Our data support a model in which the association of LptC’s transmembrane helix with LptFG creates a nonessential step that slows down the LPS transporter.
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Affiliation(s)
- Andrew Wilson
- Department of Microbiology, The Ohio State University, Columbus, Ohio, USA
| | - Natividad Ruiz
- Department of Microbiology, The Ohio State University, Columbus, Ohio, USA
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13
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Huynh MS, Hooda Y, Li YR, Jagielnicki M, Lai CCL, Moraes TF. Reconstitution of surface lipoprotein translocation through the slam translocon. eLife 2022; 11:72822. [PMID: 35475756 PMCID: PMC9090332 DOI: 10.7554/elife.72822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 04/26/2022] [Indexed: 11/13/2022] Open
Abstract
Surface lipoproteins (SLPs) are peripherally attached to the outer leaflet of the outer membrane in many Gram-negative bacteria, playing significant roles in nutrient acquisition and immune evasion in the host. While the factors that are involved in the synthesis and delivery of SLPs in the inner membrane are well characterized, the molecular machinery required for the movement of SLPs to the surface are still not fully elucidated. In this study, we investigated the translocation of a SLP TbpB through a Slam1-dependent pathway. Using purified components, we developed an in vitro translocation assay where unfolded TbpB is transported through Slam1-containing proteoliposomes, confirming Slam1 as an outer membrane translocon. While looking to identify factors to increase translocation efficiency, we discovered the periplasmic chaperone Skp interacted with TbpB in the periplasm of Escherichia coli. The presence of Skp was found to increase the translocation efficiency of TbpB in the reconstituted translocation assays. A knockout of Skp in Neisseria meningitidis revealed that Skp is essential for functional translocation of TbpB to the bacterial surface. Taken together, we propose a pathway for surface destined lipoproteins, where Skp acts as a holdase for Slam-mediated TbpB translocation across the outer membrane.
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Affiliation(s)
- Minh Sang Huynh
- Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Yogesh Hooda
- MRC Laboratory of Molecular Biology, University of Cambridge, Cambridge, United Kingdom
| | - Yuzi Raina Li
- Department of Biochemistry, University of Toronto, Toronto, Canada
| | | | | | - Trevor F Moraes
- Department of Biochemistry, University of Toronto, Toronto, Canada
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14
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Botte M, Ni D, Schenck S, Zimmermann I, Chami M, Bocquet N, Egloff P, Bucher D, Trabuco M, Cheng RKY, Brunner JD, Seeger MA, Stahlberg H, Hennig M. Cryo-EM structures of a LptDE transporter in complex with Pro-macrobodies offer insight into lipopolysaccharide translocation. Nat Commun 2022; 13:1826. [PMID: 35383177 PMCID: PMC8983717 DOI: 10.1038/s41467-022-29459-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 03/11/2022] [Indexed: 11/13/2022] Open
Abstract
Lipopolysaccharides are major constituents of the extracellular leaflet in the bacterial outer membrane and form an effective physical barrier for environmental threats and for antibiotics in Gram-negative bacteria. The last step of LPS insertion via the Lpt pathway is mediated by the LptD/E protein complex. Detailed insights into the architecture of LptDE transporter complexes have been derived from X-ray crystallography. However, no structure of a laterally open LptD transporter, a transient state that occurs during LPS release, is available to date. Here, we report a cryo-EM structure of a partially opened LptDE transporter in complex with rigid chaperones derived from nanobodies, at 3.4 Å resolution. In addition, a subset of particles allows to model a structure of a laterally fully opened LptDE complex. Our work offers insights into the mechanism of LPS insertion, provides a structural framework for the development of antibiotics targeting LptD and describes a highly rigid chaperone scaffold to enable structural biology of challenging protein targets.
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Affiliation(s)
- Mathieu Botte
- leadXpro AG, Park Innovaare, 5234, Villigen, Switzerland
| | - Dongchun Ni
- C-CINA, Biozentrum, University of Basel, Mattenstr. 24, 4058, Basel, Switzerland
| | - Stephan Schenck
- leadXpro AG, Park Innovaare, 5234, Villigen, Switzerland
- VIB-VUB Center for Structural Biology, VIB, 1050, Brussels, Belgium
| | - Iwan Zimmermann
- Institute of Medical Microbiology, University of Zürich, Gloriastasse 28/30, 8006, Zürich, Switzerland
- Linkster Therapeutics AG, 8006, Zürich, Switzerland
| | - Mohamed Chami
- C-CINA, Biozentrum, University of Basel, Mattenstr. 24, 4058, Basel, Switzerland
| | | | - Pascal Egloff
- Institute of Medical Microbiology, University of Zürich, Gloriastasse 28/30, 8006, Zürich, Switzerland
- Linkster Therapeutics AG, 8006, Zürich, Switzerland
| | - Denis Bucher
- leadXpro AG, Park Innovaare, 5234, Villigen, Switzerland
| | | | | | - Janine D Brunner
- Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute (PSI), 5232, Villigen, Switzerland
- VIB-VUB Center for Structural Biology, VIB, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, 1050, Brussels, Belgium
| | - Markus A Seeger
- Institute of Medical Microbiology, University of Zürich, Gloriastasse 28/30, 8006, Zürich, Switzerland
| | - Henning Stahlberg
- C-CINA, Biozentrum, University of Basel, Mattenstr. 24, 4058, Basel, Switzerland
| | - Michael Hennig
- leadXpro AG, Park Innovaare, 5234, Villigen, Switzerland.
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15
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Thoma J, Burmann BM. Architects of their own environment: How membrane proteins shape the Gram-negative cell envelope. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2021; 128:1-34. [PMID: 35034716 DOI: 10.1016/bs.apcsb.2021.10.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Gram-negative bacteria are surrounded by a complex multilayered cell envelope, consisting of an inner and an outer membrane, and separated by the aqueous periplasm, which contains a thin peptidoglycan cell wall. These bacteria employ an arsenal of highly specialized membrane protein machineries to ensure the correct assembly and maintenance of the membranes forming the cell envelope. Here, we review the diverse protein systems, which perform these functions in Escherichia coli, such as the folding and insertion of membrane proteins, the transport of lipoproteins and lipopolysaccharide within the cell envelope, the targeting of phospholipids, and the regulation of mistargeted envelope components. Some of these protein machineries have been known for a long time, yet still hold surprises. Others have only recently been described and some are still missing pieces or yet remain to be discovered.
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Affiliation(s)
- Johannes Thoma
- Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Göteborg, Sweden; Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden.
| | - Björn M Burmann
- Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Göteborg, Sweden; Department of Chemistry and Molecular Biology, University of Gothenburg, Göteborg, Sweden
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16
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Hawley KL, Montezuma-Rusca JM, Delgado KN, Singh N, Uversky VN, Caimano MJ, Radolf JD, Luthra A. Structural Modeling of the Treponema pallidum Outer Membrane Protein Repertoire: a Road Map for Deconvolution of Syphilis Pathogenesis and Development of a Syphilis Vaccine. J Bacteriol 2021; 203:e0008221. [PMID: 33972353 PMCID: PMC8407342 DOI: 10.1128/jb.00082-21] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/27/2021] [Indexed: 01/11/2023] Open
Abstract
Treponema pallidum, an obligate human pathogen, has an outer membrane (OM) whose physical properties, ultrastructure, and composition differ markedly from those of phylogenetically distant Gram-negative bacteria. We developed structural models for the outer membrane protein (OMP) repertoire (OMPeome) of T. pallidum Nichols using solved Gram-negative structures, computational tools, and small-angle X-ray scattering (SAXS) of selected recombinant periplasmic domains. The T. pallidum "OMPeome" harbors two "stand-alone" proteins (BamA and LptD) involved in OM biogenesis and four paralogous families involved in the influx/efflux of small molecules: 8-stranded β-barrels, long-chain-fatty-acid transporters (FadLs), OM factors (OMFs) for efflux pumps, and T. pallidum repeat proteins (Tprs). BamA (TP0326), the central component of a β-barrel assembly machine (BAM)/translocation and assembly module (TAM) hybrid, possesses a highly flexible polypeptide-transport-associated (POTRA) 1-5 arm predicted to interact with TamB (TP0325). TP0515, an LptD ortholog, contains a novel, unstructured C-terminal domain that models inside the β-barrel. T. pallidum has four 8-stranded β-barrels, each containing positively charged extracellular loops that could contribute to pathogenesis. Three of five FadL-like orthologs have a novel α-helical, presumptively periplasmic C-terminal extension. SAXS and structural modeling further supported the bipartite membrane topology and tridomain architecture of full-length members of the Tpr family. T. pallidum's two efflux pumps presumably extrude noxious small molecules via four coexpressed OMFs with variably charged tunnels. For BamA, LptD, and OMFs, we modeled the molecular machines that deliver their substrates into the OM or external milieu. The spirochete's extended families of OM transporters collectively confer a broad capacity for nutrient uptake. The models also furnish a structural road map for vaccine development. IMPORTANCE The unusual outer membrane (OM) of T. pallidum, the syphilis spirochete, is the ultrastructural basis for its well-recognized capacity for invasiveness, immune evasion, and persistence. In recent years, we have made considerable progress in identifying T. pallidum's repertoire of OMPs. Here, we developed three-dimensional (3D) models for the T. pallidum Nichols OMPeome using structural modeling, bioinformatics, and solution scattering. The OM contains three families of OMP transporters, an OMP family involved in the extrusion of noxious molecules, and two "stand-alone" proteins involved in OM biogenesis. This work represents a major advance toward elucidating host-pathogen interactions during syphilis; understanding how T. pallidum, an extreme auxotroph, obtains a wide array of biomolecules from its obligate human host; and developing a vaccine with global efficacy.
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Affiliation(s)
- Kelly L. Hawley
- Department of Pediatrics, UConn Health, Farmington, Connecticut, USA
- Division of Infectious Diseases and Immunology, Connecticut Children’s, Hartford, Connecticut, USA
| | - Jairo M. Montezuma-Rusca
- Department of Pediatrics, UConn Health, Farmington, Connecticut, USA
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Division of Infectious Diseases, UConn Health, Farmington, Connecticut, USA
| | | | - Navreeta Singh
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
| | - Vladimir N. Uversky
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Melissa J. Caimano
- Department of Pediatrics, UConn Health, Farmington, Connecticut, USA
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
| | - Justin D. Radolf
- Department of Pediatrics, UConn Health, Farmington, Connecticut, USA
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
- Department of Genetics and Genome Sciences, UConn Health, Farmington, Connecticut, USA
- Department of Immunology, UConn Health, Farmington, Connecticut, USA
| | - Amit Luthra
- Department of Medicine, UConn Health, Farmington, Connecticut, USA
- Department of Molecular Biology and Biophysics, UConn Health, Farmington, Connecticut, USA
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17
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Abstract
The outer membrane of Gram-negative bacteria is essential for their survival in harsh environments and provides intrinsic resistance to many antibiotics. This membrane is remarkable; it is a highly asymmetric lipid bilayer. The inner leaflet of the outer membrane contains phospholipids, whereas the fatty acyl chains attached to lipopolysaccharide (LPS) comprise the hydrophobic portion of the outer leaflet. This lipid asymmetry, and in particular the exclusion of phospholipids from the outer leaflet, is key to creating an almost impenetrable barrier to hydrophobic molecules that can otherwise pass through phospholipid bilayers. It has long been known that these lipids are not made in the outer membrane. It is now believed that conserved multisubunit protein machines extract these lipids after their synthesis is completed at the inner membrane and transport them to the outer membrane. A longstanding question is how the cell builds and maintains this asymmetric lipid bilayer in coordination with the assembly of the other components of the cell envelope. This Review describes the trans-envelope lipid transport systems that have been identified to participate in outer-membrane biogenesis: LPS transport via the Lpt machine, and phospholipid transport via the Mla pathway and several recently proposed transporters.
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Affiliation(s)
| | - Daniel Kahne
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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18
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Synthesis and delivery of Streptococcus pneumoniae capsular polysaccharides by recombinant attenuated Salmonella vaccines. Proc Natl Acad Sci U S A 2021; 118:2013350118. [PMID: 33380455 PMCID: PMC7812815 DOI: 10.1073/pnas.2013350118] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Pneumococcal infection-caused diseases are responsible for substantial morbidity and mortality worldwide. Traditional pneumococcal vaccines are developed based on purified capsular polysaccharides (CPS) or CPS conjugated to a protein carrier. Production processes of the traditional vaccines are laborious, and thereby increase the vaccine cost and limit their use in developing nations. A cost-effective pneumococcal vaccine using the recombinant attenuated Salmonella vaccine (RASV) was developed in this study. We cloned and expressed genes for seven serotypes of CPSs in the RASV strain. The RASV-delivered CPSs induced robust humoral and cell-mediated responses and mediated efficient protection of mice against pneumococcal infection. Our work provides an innovative strategy for mass producing low-cost bioconjugated polysaccharide vaccines for needle-free mucosal delivery against pneumococcal infections. Streptococcus pneumoniae capsular polysaccharides (CPSs) are major determinants of bacterial pathogenicity. CPSs of different serotypes form the main components of the pneumococcal vaccines Pneumovax, Prevnar7, and Prevnar13, which substantially reduced the S. pneumoniae disease burden in developed countries. However, the laborious production processes of traditional polysaccharide-based vaccines have raised the cost of the vaccines and limited their impact in developing countries. The aim of this study is to develop a kind of low-cost live vaccine based on using the recombinant attenuated Salmonella vaccine (RASV) system to protect against pneumococcal infections. We cloned genes for seven different serotypes of CPSs to be expressed by the RASV strain. Oral immunization of mice with the RASV-CPS strains elicited robust Th1 biased adaptive immune responses. All the CPS-specific antisera mediated opsonophagocytic killing of the corresponding serotype of S. pneumoniae in vitro. The RASV-CPS2 and RASV-CPS3 strains provided efficient protection of mice against challenge infections with either S. pneumoniae strain D39 or WU2. Synthesis and delivery of S. pneumoniae CPSs using the RASV strains provide an innovative strategy for low-cost pneumococcal vaccine development, production, and use.
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19
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Mass spectrometry informs the structure and dynamics of membrane proteins involved in lipid and drug transport. Curr Opin Struct Biol 2021; 70:53-60. [PMID: 33964676 DOI: 10.1016/j.sbi.2021.03.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 03/30/2021] [Indexed: 12/15/2022]
Abstract
Membrane proteins are important macromolecules that play crucial roles in many cellular and physiological processes. Over the past two decades, the use of mass spectrometry as a biophysical tool to characterise membrane proteins has grown steadily. By capturing these dynamic complexes in the gas phase, many unknown small molecule interactions have been revealed. One particular application of this research has been the focus on antibiotic resistance with considerable efforts being made to understand underlying mechanisms. Here we review recent advances in the application of mass spectrometry that have yielded both structural and dynamic information on the interactions of antibiotics with proteins involved in bacterial cell envelope biogenesis and drug efflux.
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20
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Roumia AF, Tsirigos KD, Theodoropoulou MC, Tamposis IA, Hamodrakas SJ, Bagos PG. OMPdb: A Global Hub of Beta-Barrel Outer Membrane Proteins. FRONTIERS IN BIOINFORMATICS 2021; 1:646581. [PMID: 36303794 PMCID: PMC9581022 DOI: 10.3389/fbinf.2021.646581] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Accepted: 03/18/2021] [Indexed: 11/14/2022] Open
Abstract
OMPdb (www.ompdb.org) was introduced as a database for β-barrel outer membrane proteins from Gram-negative bacteria in 2011 and then included 69,354 entries classified into 85 families. The database has been updated continuously using a collection of characteristic profile Hidden Markov Models able to discriminate between the different families of prokaryotic transmembrane β-barrels. The number of families has increased ultimately to a total of 129 families in the current, second major version of OMPdb. New additions have been made in parallel with efforts to update existing families and add novel families. Here, we present the upgrade of OMPdb, which from now on aims to become a global repository for all transmembrane β-barrel proteins, both eukaryotic and bacterial.
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Affiliation(s)
- Ahmed F. Roumia
- Department of Computer Science and Biomedical Informatics, University of Thessaly, Lamia, Greece
| | | | | | - Ioannis A. Tamposis
- Department of Computer Science and Biomedical Informatics, University of Thessaly, Lamia, Greece
| | - Stavros J. Hamodrakas
- Section of Cell Biology and Biophysics, Department of Biology, School of Sciences, National and Kapodistrian University of Athens, Athens, Greece
| | - Pantelis G. Bagos
- Department of Computer Science and Biomedical Informatics, University of Thessaly, Lamia, Greece
- *Correspondence: Pantelis G. Bagos
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21
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Li L, Li R, Qi C, Gao H, Wei Q, Tan L, Sun F. Mechanisms of polymyxin resistance induced by Salmonella typhimurium in vitro. Vet Microbiol 2021; 257:109063. [PMID: 33932721 DOI: 10.1016/j.vetmic.2021.109063] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 03/29/2021] [Indexed: 11/26/2022]
Abstract
The increase incidence of multi-drug resistant (MDR) Salmonella has become a major global health concern. Polymyxin, an ancient polypeptide antibiotic, has been given renewed attention over recent years, resulting in resistance of Gram-negative bacteria to polymyxin, but its resistance mechanism is not completely clear. Thus, it is important to study its resistance mechanisms. In this study, an in vitro induced polymyxin-resistant strain of Salmonella typhimurium in the laboratory were constructed to investigate the mechanism of resistance of Salmonella to polymyxin. Gradual induction of Salmonella typhimurium ATCC13311 (AT) by concentration increment was used to screen for a highly polymyxin-resistant strain AT-P128. The broth dilution technique was used to compare the sensitivity of the two strains to different antimicrobial drugs. Single nucleotide polymorphisms (SNPs) were then identified by whole genome sequencing, and differences in gene expression between the two strains were compared by transcriptome sequencing and reverse transcription-quantitative PCR (RT-qPCR). Finally, for the first time, the CRISPR/Cas9 gene-editing system was used to construct gene deletion mutants in Salmonella to knock out the phoP gene of AT-P128. The results showed that strain AT-P128 was significantly more resistant to amoxicillin, ceftiofur, ampicillin, fluphenazine, and chloramphenicol and significantly less resistant to sulfamethoxazole than the parental strain AT. The growth curve results showed no significant change in the growth rate between AT-P128 and AT. Motility and biofilm formation assays showed a significant decrease in AT-P128. Additionally, the WGS results showed that AT-P128 had mutations in 9 genes involving 14 SNPs. RNA-seq and RT-qPCR results showed increased expression of phoPQ. The loss of the phoP gene decreased AT-P128ΔphoP resistance to polymyxin by 32-fold. These results suggested that polymyxin resistance affected the biology, genome components, and gene expression levels of Salmonella and that the PhoPQ two-component system played a key role in polymyxin resistance in Salmonella, providing insights into the diversity and complexity of polymyxin resistance in Salmonella.
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Affiliation(s)
- Lin Li
- Pharmacology and Toxicology Laboratory, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui 230026, PR China; Anhui Province Key Lab of Veterinary Pathobiology and Disease Control, Anhui Agricultural University, Hefei, Anhui 230036, PR China
| | - Rui Li
- Pharmacology and Toxicology Laboratory, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui 230026, PR China
| | - Caili Qi
- Pharmacology and Toxicology Laboratory, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui 230026, PR China
| | - Haixia Gao
- Pharmacology and Toxicology Laboratory, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui 230026, PR China
| | - Qiling Wei
- Pharmacology and Toxicology Laboratory, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui 230026, PR China
| | - Lei Tan
- Pharmacology and Toxicology Laboratory, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui 230026, PR China
| | - Feifei Sun
- Pharmacology and Toxicology Laboratory, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui 230026, PR China; Anhui Province Key Lab of Veterinary Pathobiology and Disease Control, Anhui Agricultural University, Hefei, Anhui 230036, PR China.
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22
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Guest RL, Rutherford ST, Silhavy TJ. Border Control: Regulating LPS Biogenesis. Trends Microbiol 2021; 29:334-345. [PMID: 33036869 PMCID: PMC7969359 DOI: 10.1016/j.tim.2020.09.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 09/11/2020] [Accepted: 09/14/2020] [Indexed: 12/20/2022]
Abstract
The outer membrane (OM) is a defining feature of Gram-negative bacteria that serves as a permeability barrier and provides rigidity to the cell. Critical to OM function is establishing and maintaining an asymmetrical bilayer structure with phospholipids in the inner leaflet and the complex glycolipid lipopolysaccharide (LPS) in the outer leaflet. Cells ensure this asymmetry by regulating the biogenesis of lipid A, the conserved and essential anchor of LPS. Here we review the consequences of disrupting the regulatory components that control lipid A biogenesis, focusing on the rate-limiting step performed by LpxC. Dissection of these processes provides critical insights into bacterial physiology and potential new targets for antibiotics able to overcome rapidly spreading resistance mechanisms.
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Affiliation(s)
- Randi L Guest
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Steven T Rutherford
- Department of Infectious Diseases, Genentech Inc., South San Francisco, CA, USA
| | - Thomas J Silhavy
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
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23
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Walker SS, Black TA. Are outer-membrane targets the solution for MDR Gram-negative bacteria? Drug Discov Today 2021; 26:2152-2158. [PMID: 33798647 DOI: 10.1016/j.drudis.2021.03.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 02/27/2021] [Accepted: 03/23/2021] [Indexed: 01/17/2023]
Abstract
The outer membrane (OM) of Gram-negative bacteria confers a significant barrier to many antibacterial agents targeting periplasmic and cytosolic functions. 'Synergist' approaches to disrupt the OM have been hampered by poor specificity and accompanying toxicities. The OM contains proteins required for optimal growth and pathogenesis, including lipopolysaccharide (LPS) and capsular polysaccharide (CPS) transport, porins for uptake of macromolecules, and transporters for essential elements (such as iron). Does the external proximity of these proteins offer an enhanced potential to identify effective therapies? Here, we review recent experiences in exploiting Gram-negative OM proteins (OMPs) to address the calamity of exploding antimicrobial resistance. Teaser: Multidrug-resistant (MDR) Gram-negative bacteria are a growing crisis. Few new antimicrobial chemotypes or targets have been identified after decades of screening. Are OMP targets a solution to MDR Gram-negative bacteria?
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Affiliation(s)
- Scott S Walker
- Infectious Diseases and Vaccines Basic Research, Merck & Co., Inc, 770 Sumneytown Pike, West Point, PA 19486, USA
| | - Todd A Black
- Infectious Diseases and Vaccines Basic Research, Merck & Co., Inc, 770 Sumneytown Pike, West Point, PA 19486, USA.
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24
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Lundstedt EA, Simpson BW, Ruiz N. Lipopolysaccharide transport involves long-range coupling between cytoplasmic and periplasmic domains of the LptB 2FGC extractor. J Bacteriol 2020; 203:JB.00618-20. [PMID: 33361195 PMCID: PMC8095461 DOI: 10.1128/jb.00618-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 12/18/2020] [Indexed: 01/04/2023] Open
Abstract
The cell surface of the Gram-negative cell envelope contains lipopolysaccharide (LPS) molecules, which form a permeability barrier against hydrophobic antibiotics. The LPS transport (Lpt) machine composed of LptB2FGCADE forms a proteinaceous trans-envelope bridge that allows for the rapid and specific transport of newly synthesized LPS from the inner membrane (IM) to the outer membrane (OM). This transport is powered from the IM by the ATP-binding cassette transporter LptB2FGC. The ATP-driven cycling between closed- and open-dimer states of the ATPase LptB2 is coupled to the extraction of LPS by the transmembrane domains LptFG. However, the mechanism by which LPS moves from a substrate-binding cavity formed by LptFG at the IM to the first component of the periplasmic bridge, the periplasmic β-jellyroll domain of LptF, is poorly understood. To better understand how LptB2FGC functions in Escherichia coli, we searched for suppressors of a defective LptB variant. We found that defects in LptB2 can be suppressed by both structural modifications to the core oligosaccharide of LPS and changes in various regions of LptFG, including a periplasmic loop in LptF that connects the substrate-binding cavity in LptFG to the periplasmic β-jellyroll domain of LptF. These novel suppressors suggest that interactions between the core oligosaccharide of LPS and periplasmic regions in the transporter influence the rate of LPS extraction by LptB2FGC. Together, our genetic data reveal a path for the bi-directional coupling between LptB2 and LptFG that extends from the cytoplasm to the entrance to the periplasmic bridge of the transporter.IMPORTANCEGram-negative bacteria are intrinsically resistant to many antibiotics due to the presence of lipopolysaccharide (LPS) at their cell surface. LPS is transported from its site of synthesis at the inner membrane to the outer membrane by the Lpt machine. Lpt proteins form a transporter that spans the entire envelope and is thought to function similarly to a PEZ candy dispenser. This trans-envelope machine is powered by the cytoplasmic LptB ATPase through a poorly understood mechanism. Using genetic analyses in Escherichia coli, we found that LPS transport involves long-ranging bi-directional coupling across cellular compartments between cytoplasmic LptB and periplasmic regions of the Lpt transporter. This knowledge could be exploited in developing antimicrobials that overcome the permeability barrier imposed by LPS.
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Affiliation(s)
- Emily A Lundstedt
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
| | - Brent W Simpson
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
| | - Natividad Ruiz
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
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25
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Dynamics of an LPS translocon induced by substrate and an antimicrobial peptide. Nat Chem Biol 2020; 17:187-195. [PMID: 33199913 DOI: 10.1038/s41589-020-00694-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 10/12/2020] [Indexed: 01/11/2023]
Abstract
Lipopolysaccharide (LPS) transport to the outer membrane (OM) is a crucial step in the biogenesis of microbial surface defenses. Although many features of the translocation mechanism have been elucidated, molecular details of LPS insertion via the LPS transport (Lpt) OM protein LptDE remain elusive. Here, we integrate native MS with hydrogen-deuterium exchange MS and molecular dynamics simulations to investigate the influence of substrate and peptide binding on the conformational dynamics of LptDE. Our data reveal that LPS induces opening of the LptD β-taco domain, coupled with conformational changes on β-strands adjacent to the putative lateral exit gate. Conversely, an antimicrobial peptide, thanatin, stabilizes the β-taco, thereby preventing LPS transport. Our results illustrate that LPS insertion into the OM relies on concerted opening movements of both the β-barrel and β-taco domains of LptD, and suggest a means for developing antimicrobial therapeutics targeting this essential process in Gram-negative ESKAPE pathogens.
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26
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Horne JE, Brockwell DJ, Radford SE. Role of the lipid bilayer in outer membrane protein folding in Gram-negative bacteria. J Biol Chem 2020; 295:10340-10367. [PMID: 32499369 PMCID: PMC7383365 DOI: 10.1074/jbc.rev120.011473] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 06/03/2020] [Indexed: 01/09/2023] Open
Abstract
β-Barrel outer membrane proteins (OMPs) represent the major proteinaceous component of the outer membrane (OM) of Gram-negative bacteria. These proteins perform key roles in cell structure and morphology, nutrient acquisition, colonization and invasion, and protection against external toxic threats such as antibiotics. To become functional, OMPs must fold and insert into a crowded and asymmetric OM that lacks much freely accessible lipid. This feat is accomplished in the absence of an external energy source and is thought to be driven by the high thermodynamic stability of folded OMPs in the OM. With such a stable fold, the challenge that bacteria face in assembling OMPs into the OM is how to overcome the initial energy barrier of membrane insertion. In this review, we highlight the roles of the lipid environment and the OM in modulating the OMP-folding landscape and discuss the factors that guide folding in vitro and in vivo We particularly focus on the composition, architecture, and physical properties of the OM and how an understanding of the folding properties of OMPs in vitro can help explain the challenges they encounter during folding in vivo Current models of OMP biogenesis in the cellular environment are still in flux, but the stakes for improving the accuracy of these models are high. OMP folding is an essential process in all Gram-negative bacteria, and considering the looming crisis of widespread microbial drug resistance it is an attractive target. To bring down this vital OMP-supported barrier to antibiotics, we must first understand how bacterial cells build it.
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Affiliation(s)
- Jim E Horne
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - David J Brockwell
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
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27
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Baral B, Mozafari MR. Strategic Moves of "Superbugs" Against Available Chemical Scaffolds: Signaling, Regulation, and Challenges. ACS Pharmacol Transl Sci 2020; 3:373-400. [PMID: 32566906 PMCID: PMC7296549 DOI: 10.1021/acsptsci.0c00005] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Indexed: 12/12/2022]
Abstract
Superbugs' resistivity against available natural products has become an alarming global threat, causing a rapid deterioration in public health and claiming tens of thousands of lives yearly. Although the rapid discovery of small molecules from plant and microbial origin with enhanced bioactivity has provided us with some hope, a rapid hike in the resistivity of superbugs has proven to be the biggest therapeutic hurdle of all times. Moreover, several distinct mechanisms endowed by these notorious superbugs make them immune to these antibiotics subsequently causing our antibiotic wardrobe to be obsolete. In this unfortunate situation, though the time frame for discovering novel "hit molecules" down the line remains largely unknown, our small hope and untiring efforts injected in hunting novel chemical scaffolds with unique molecular targets using high-throughput technologies may safeguard us against these life-threatening challenges to some extent. Amid this crisis, the current comprehensive review highlights the present status of knowledge, our search for bacteria Achilles' heel, distinct molecular signaling that an opportunistic pathogen bestows to trespass the toxicity of antibiotics, and facile strategies and appealing therapeutic targets of novel drugs. Herein, we also discuss multidimensional strategies to combat antimicrobial resistance.
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Affiliation(s)
- Bikash Baral
- Department
of Biochemistry, University of Turku, Tykistökatu 6, Turku, Finland
| | - M. R. Mozafari
- Australasian
Nanoscience and Nanotechnology Initiative, 8054 Monash University LPO, Clayton, Victoria 3168, Australia
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28
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Liu Q, Su H, Bian X, Wang S, Kong Q. Live attenuated Salmonella Typhimurium with monophosphoryl lipid A retains ability to induce T-cell and humoral immune responses against heterologous polysaccharide of Shigella flexneri 2a. Int J Med Microbiol 2020; 310:151427. [PMID: 32654768 DOI: 10.1016/j.ijmm.2020.151427] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 05/03/2020] [Accepted: 05/10/2020] [Indexed: 12/19/2022] Open
Abstract
Shigella flexneri 2a (Sf2a) is one of the most frequently isolated Shigella strains that causes the endemic shigellosis in developing countries. In this study, we used recombinant attenuated Salmonella vaccine (RASV) strains to deliver Sf2a O-antigen and characterized the immune responses induced by the vectored O-antigen. First, we identified genes sufficient for biosynthesis of Sf2a O-antigen. A plasmid containing the identified genes was then introduced into the RASV strains, which were manipulated to produce only the heterologous O-antigen and modified lipid A. After oral immunization of mice, we demonstrated that RASV strains could induce potent humoral immune responses as well as robust CD4+ T-cell responses against Sf2a Lipopolysaccharide (LPS) and protect mice against virulent Sf2a challenge. The induced serum antibodies mediated high levels of Shigella-specific serum bactericidal activity and C3 deposition. Moreover, the IgG+ B220low/int BM cell and T follicular helper (Tfh) cell responses could also be triggered effectively. The live attenuated Salmonella with the modified lipid A delivering Sf2a O-antigen polysaccharide showed the same ability to induce immune responses against Sf2a LPS as the strain with the original lipid A. These findings underscore the potential of RASV delivered Sf2a O-antigen for induction of robust CD4+ T-cell and IgG responses and warrant further studies toward the development of Shigella vaccine candidates with RASV strains.
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Affiliation(s)
- Qing Liu
- College of Animal Science and Technology, Southwest University, 400715, Chongqing, China
| | - Huali Su
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, Gainesville, 32611, FL, USA
| | - Xiaoping Bian
- College of Animal Science and Technology, Southwest University, 400715, Chongqing, China
| | - Shifeng Wang
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, Gainesville, 32611, FL, USA
| | - Qingke Kong
- College of Animal Science and Technology, Southwest University, 400715, Chongqing, China; Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, Gainesville, 32611, FL, USA.
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Riquelme SA, Wong Fok Lung T, Prince A. Pulmonary Pathogens Adapt to Immune Signaling Metabolites in the Airway. Front Immunol 2020; 11:385. [PMID: 32231665 PMCID: PMC7082326 DOI: 10.3389/fimmu.2020.00385] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 02/18/2020] [Indexed: 12/17/2022] Open
Abstract
A limited number of pulmonary pathogens are able to evade normal mucosal defenses to establish acute infection and then adapt to cause chronic pneumonias. Pathogens, such as Pseudomonas aeruginosa or Staphylococcus aureus, are typically associated with infection in patients with underlying pulmonary disease or damage, such as cystic fibrosis (CF) or chronic obstructive pulmonary disease (COPD). To establish infection, bacteria express a well-defined set of so-called virulence factors that facilitate colonization and activate an immune response, gene products that have been identified in murine models. Less well-understood are the adaptive changes that occur over time in vivo, enabling the organisms to evade innate and adaptive immune clearance mechanisms. These colonizers proliferate, generating a population sufficient to provide selection for mutants, such as small colony variants and mucoid variants, that are optimized for long term infection. Such host-adapted strains have evolved in response to selective pressure such as antibiotics and the recruitment of phagocytes at sites of infection and their release of signaling metabolites (e.g., succinate). These metabolites can potentially function as substrates for bacterial growth and but also generate oxidant stress. Whole genome sequencing and quantified expression of selected genes have helped to explain how P. aeruginosa and S. aureus adapt to the presence of these metabolites over the course of in vivo infection. The serial isolation of clonally related strains from patients with cystic fibrosis has provided the opportunity to identify bacterial metabolic pathways that are altered under this immune pressure, such as the anti-oxidant glyoxylate and pentose phosphate pathways, routes contributing to the generation of biofilms. These metabolic pathways and biofilm itself enable the organisms to dissipate oxidant stress, while providing protection from phagocytosis. Stimulation of host immune signaling metabolites by these pathogens drives bacterial adaptation and promotes their persistence in the airways. The inherent metabolic flexibility of P. aeruginosa and S. aureus is a major factor in their success as pulmonary pathogens.
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Affiliation(s)
- Sebastián A Riquelme
- Department of Pediatrics, Columbia University Medical Center, New York, NY, United States
| | - Tania Wong Fok Lung
- Department of Pediatrics, Columbia University Medical Center, New York, NY, United States
| | - Alice Prince
- Department of Pediatrics, Columbia University Medical Center, New York, NY, United States
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30
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Patro LPP, Rathinavelan T. Targeting the Sugary Armor of Klebsiella Species. Front Cell Infect Microbiol 2019; 9:367. [PMID: 31781512 PMCID: PMC6856556 DOI: 10.3389/fcimb.2019.00367] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Accepted: 10/09/2019] [Indexed: 12/25/2022] Open
Abstract
The emergence of multidrug-resistant strains of Gram-negative Klebsiella species is an urgent global threat. The World Health Organization has listed Klebsiella pneumoniae as one of the global priority pathogens in critical need of next-generation antibiotics. Compared to other Gram-negative pathogens, K. pneumoniae accumulates a greater diversity of antimicrobial-resistant genes at a higher frequency. The evolution of a hypervirulent phenotype of K. pneumoniae is yet another concern. It has a broad ecological distribution affecting humans, agricultural animals, plants, and aquatic animals. Extracellular polysaccharides of Klebsiella, such as lipopolysaccharides, capsular polysaccharides, and exopolysaccharides, play crucial roles in conferring resistance against the host immune response, as well as in colonization, surface adhesion, and for protection against antibiotics and bacteriophages. These extracellular polysaccharides are major virulent determinants and are highly divergent with respect to their antigenic properties. Wzx/Wzy-, ABC-, and synthase-dependent proteinaceous nano-machineries are involved in the biosynthesis, transport, and cell surface expression of these sugar molecules. Although the proteins involved in the biosynthesis and surface expression of these sugar molecules represent potential drug targets, variation in the amino acid sequences of some of these proteins, in combination with diversity in their sugar composition, poses a major challenge to the design of a universal drug for Klebsiella infections. This review discusses the challenges in universal Klebsiella vaccine and drug development from the perspective of antigen sugar compositions and the proteins involved in extracellular antigen transport.
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31
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Cryo-EM structures of lipopolysaccharide transporter LptB 2FGC in lipopolysaccharide or AMP-PNP-bound states reveal its transport mechanism. Nat Commun 2019; 10:4175. [PMID: 31519889 PMCID: PMC6744409 DOI: 10.1038/s41467-019-11977-1] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Accepted: 08/09/2019] [Indexed: 02/05/2023] Open
Abstract
Lipopolysaccharides (LPS) of Gram-negative bacteria are critical for the defence against cytotoxic substances and must be transported from the inner membrane (IM) to the outer membrane (OM) through a bridge formed by seven membrane proteins (LptBFGCADE). The IM component LptB2FG powers the process through a yet unclarified mechanism. Here we report three high-resolution cryo-EM structures of LptB2FG alone and complexed with LptC (LptB2FGC), trapped in either the LPS- or AMP-PNP-bound state. The structures reveal conformational changes between these states and substrate binding with or without LptC. We identify two functional transmembrane arginine-containing loops interacting with the bound AMP-PNP and elucidate allosteric communications between the domains. AMP-PNP binding induces an inward rotation and shift of the transmembrane helices of LptFG and LptC to tighten the cavity, with the closure of two lateral gates, to eventually expel LPS into the bridge. Functional assays reveal the functionality of the LptF and LptG periplasmic domains. Our findings shed light on the LPS transport mechanism. Seven lipopolysaccharide (LPS) transport proteins (LptBFGCADE) mediate the transport of LPS from the inner to the outer membrane of Gram-negative bacteria. Here the authors provide mechanistic insights into LPS recognition and transportation by determining the cryo-EM structures of the inner membrane complex LptB2FGC bound to either LPS or AMP-PNP.
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32
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Intermembrane transport: Glycerophospholipid homeostasis of the Gram-negative cell envelope. Proc Natl Acad Sci U S A 2019; 116:17147-17155. [PMID: 31420510 PMCID: PMC6717313 DOI: 10.1073/pnas.1902026116] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
This perspective addresses recent advances in lipid transport across the Gram-negative inner and outer membranes. While we include a summary of previously existing literature regarding this topic, we focus on the maintenance of lipid asymmetry (Mla) pathway. Discovered in 2009 by the Silhavy group [J. C. Malinverni, T. J. Silhavy, Proc. Natl. Acad. Sci. U.S.A. 106, 8009–8014 (2009)], Mla has become increasingly appreciated for its role in bacterial cell envelope physiology. Through the work of many, we have gained an increasingly mechanistic understanding of the function of Mla via genetic, biochemical, and structural methods. Despite this, there is a degree of controversy surrounding the directionality in which Mla transports lipids. While the initial discovery and subsequent studies have posited that it mediated retrograde lipid transport (removing glycerophospholipids from the outer membrane and returning them to the inner membrane), others have asserted the opposite. This Perspective aims to lay out the evidence in an unbiased, yet critical, manner for Mla-mediated transport in addition to postulation of mechanisms for anterograde lipid transport from the inner to outer membranes.
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33
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Lundquist KP, Gumbart JC. Presence of substrate aids lateral gate separation in LptD. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183025. [PMID: 31351059 DOI: 10.1016/j.bbamem.2019.07.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 06/25/2019] [Accepted: 07/14/2019] [Indexed: 10/26/2022]
Abstract
Lipopolysaccharides (LPS) provide the outer membrane (OM) of Gram-negative bacteria with a strong protective barrier. The periplasm-spanning Lpt machinery is responsible for the transport of LPS molecules across the periplasm, culminating in insertion by the outer-membrane proteins LptD and LptE. In order to elucidate the mechanisms of LPS insertion by LptDE, we performed over 14 microseconds of equilibrium molecular dynamics simulations. Bilayer-dependent differences in the fluctuations and secondary structure of LptD's extracellular loops are observed for a pure DMPE membrane vs. a model of the OM. Furthermore, LptD's periplasmic N-terminal domain is highly dynamic, which may help to maintain the integrity of the periplasm-spanning complex amidst relative motion of the inner-membrane and outer-membrane anchored domains. In addition, our simulations demonstrate that binding of LPS substrate activates a switching between the associated and dissociated states of two lumenal loops at the interface between the β-barrel and the N-terminal domain as well as LptD's lateral gate on the microsecond timescale, neither of which is observed for the apo state. Placement of a substrate LPS molecule also causes an increase in the average separation of the LptD lateral gate strands and a lowering of the energetic barrier to lateral gate opening.
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Affiliation(s)
- Karl P Lundquist
- School of Physics, Georgia Institute of Technology, Atlanta, GA 30313, United States of America
| | - James C Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, GA 30313, United States of America.
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Storek KM, Chan J, Vij R, Chiang N, Lin Z, Bevers J, Koth CM, Vernes JM, Meng YG, Yin J, Wallweber H, Dalmas O, Shriver S, Tam C, Schneider K, Seshasayee D, Nakamura G, Smith PA, Payandeh J, Koerber JT, Comps-Agrar L, Rutherford ST. Massive antibody discovery used to probe structure-function relationships of the essential outer membrane protein LptD. eLife 2019; 8:46258. [PMID: 31237236 PMCID: PMC6592684 DOI: 10.7554/elife.46258] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 05/17/2019] [Indexed: 12/17/2022] Open
Abstract
Outer membrane proteins (OMPs) in Gram-negative bacteria dictate permeability of metabolites, antibiotics, and toxins. Elucidating the structure-function relationships governing OMPs within native membrane environments remains challenging. We constructed a diverse library of >3000 monoclonal antibodies to assess the roles of extracellular loops (ECLs) in LptD, an essential OMP that inserts lipopolysaccharide into the outer membrane of Escherichia coli. Epitope binning and mapping experiments with LptD-loop-deletion mutants demonstrated that 7 of the 13 ECLs are targeted by antibodies. Only ECLs inaccessible to antibodies were required for the structure or function of LptD. Our results suggest that antibody-accessible loops evolved to protect key extracellular regions of LptD, but are themselves dispensable. Supporting this hypothesis, no α-LptD antibody interfered with essential functions of LptD. Our experimental workflow enables structure-function studies of OMPs in native cellular environments, provides unexpected insight into LptD, and presents a method to assess the therapeutic potential of antibody targeting. The overuse and misuse of antibiotics has led to the rise of multi-drug resistant bacteria which threaten global public health. Antibiotics interfere with essential processes in bacteria so they are unable to divide or survive, but over time, the microbes have found ways to become immune to the drugs. New antibiotics are now desperately needed. Gram-negative bacteria are wrapped in an outer membrane made of large molecules called lipopolysaccharides. This structure is an extra barrier to molecules (such as drugs) that try to enter the cell, but it could also hold new targets for antibiotics to exploit. A protein called LptD is embedded in the outer membrane, where it inserts new lipopolysaccharides. It is critical for bacteria to grow and survive, and is a relatively new potential target for antibiotic development. The protein has a number of ‘extracellular loops’ that extend into the environment, but their roles in the structure and the activity of LptD are still largely unknown. This is partly due to a lack of tools to investigate these elements. In response, Storek et al. built a library of over 3,000 custom antibodies, which are small Y-shaped proteins that can each recognise a specific portion in one of the extracellular loops and potentially incapacitate LptD. The antibodies were used to target LptD in its native environment, when it is embedded in the bacteria. In parallel, mutant bacteria were created in which the loops were genetically removed one by one to assess their importance for LptD activity. The experiments revealed that although the antibodies could target most extracellular loops, they could not target the few loops that were essential for LptD to work properly. This suggests that antibody-accessible loops are expendable and that these structures could serve to shield other regions of LptD which are critical for survival. The findings will help to prioritise research that develops other approaches to inhibit LptD. Finally, the antibody workflow designed by Storek et al. can serve as a road map to study other membrane proteins in their native cellular environment.
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Affiliation(s)
- Kelly M Storek
- Department of Infectious Diseases, Genentech, Inc, South San Francisco, United States
| | - Joyce Chan
- Department of Biochemical and Cellular Pharmacology, Genentech, Inc, South San Francisco, United States
| | - Rajesh Vij
- Department of Antibody Engineering, Genentech, Inc, South San Francisco, United States
| | - Nancy Chiang
- Department of Antibody Engineering, Genentech, Inc, South San Francisco, United States
| | - Zhonghua Lin
- Department of Antibody Engineering, Genentech, Inc, South San Francisco, United States
| | - Jack Bevers
- Department of Antibody Engineering, Genentech, Inc, South San Francisco, United States
| | - Christopher M Koth
- Department of Structural Biology, Genentech, Inc, South San Francisco, United States
| | - Jean-Michel Vernes
- Department of Biochemical and Cellular Pharmacology, Genentech, Inc, South San Francisco, United States
| | - Y Gloria Meng
- Department of Biochemical and Cellular Pharmacology, Genentech, Inc, South San Francisco, United States
| | - JianPing Yin
- Department of Structural Biology, Genentech, Inc, South San Francisco, United States
| | - Heidi Wallweber
- Department of Structural Biology, Genentech, Inc, South San Francisco, United States
| | - Olivier Dalmas
- Department of Structural Biology, Genentech, Inc, South San Francisco, United States
| | - Stephanie Shriver
- Department of Biomolecular Resources, Genentech, Inc, South San Francisco, United States
| | - Christine Tam
- Department of Biomolecular Resources, Genentech, Inc, South San Francisco, United States
| | - Kellen Schneider
- Department of Antibody Engineering, Genentech, Inc, South San Francisco, United States
| | - Dhaya Seshasayee
- Department of Antibody Engineering, Genentech, Inc, South San Francisco, United States
| | - Gerald Nakamura
- Department of Antibody Engineering, Genentech, Inc, South San Francisco, United States
| | - Peter A Smith
- Department of Infectious Diseases, Genentech, Inc, South San Francisco, United States
| | - Jian Payandeh
- Department of Structural Biology, Genentech, Inc, South San Francisco, United States
| | - James T Koerber
- Department of Antibody Engineering, Genentech, Inc, South San Francisco, United States
| | - Laetitia Comps-Agrar
- Department of Biochemical and Cellular Pharmacology, Genentech, Inc, South San Francisco, United States
| | - Steven T Rutherford
- Department of Infectious Diseases, Genentech, Inc, South San Francisco, United States
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35
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Huang L, Wang M, Mo T, Liu M, Biville F, Zhu D, Jia R, Chen S, Zhao X, Yang Q, Wu Y, Zhang S, Huang J, Tian B, Liu Y, Zhang L, Yu Y, Pan L, Rehman MU, Chen X, Cheng A. Role of LptD in Resistance to Glutaraldehyde and Pathogenicity in Riemerella anatipestifer. Front Microbiol 2019; 10:1443. [PMID: 31281307 PMCID: PMC6598057 DOI: 10.3389/fmicb.2019.01443] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2019] [Accepted: 06/07/2019] [Indexed: 11/25/2022] Open
Abstract
Riemerella anatipestifer is a gram-negative bacterium that causes disease in ducks and other birds. Despite being an important pathogen in poultry, the pathogenesis and drug resistance mechanisms of this bacterium are poorly understood. An analysis of our unpublished RNA-Seq data showed that lptD, a gene encoding one of the lipopolysaccharide transport components, is transcribed at higher levels in strain CH-1 than in strain ATCC11845. In addition, strain CH-1 has been shown to display broader drug resistance than strain ATCC11845. Since LptD is involved in LPS biogenesis and drug resistance, we wondered if lptD is associated with increased R. anatipestifer resistance to glutaraldehyde, a disinfectant used in the production industry. In this study, the minimal inhibitory concentration (MIC) of glutaraldehyde for strain CH-1 was determined to be 0.125% (vol/vol), whereas an MIC of 0.05% (vol/vol) was observed for strain ATCC11845. Furthermore, the level of lptD transcription in strain CH-1 was consistently 2-fold higher than that observed in strain ATCC11845. Moreover, lptD transcription was upregulated in both strains at a subinhibitory concentration of glutaraldehyde. The role of lptD in R. anatipestifer was further assessed by constructing an ATCC11845 mutant strain with low lptD expression, R. anatipestifer ATCC11845 lptD−. The growth of R. anatipestifer ATCC11845 lptD− was severely impaired, and this strain was more susceptible than the wild-type strain to glutaraldehyde. Moreover, compared to the wild-type strain, R. anatipestifer ATCC11845 lptD− exhibited decreased biofilm formation and was more sensitive to duck serum. Finally, low lptD expression led to decreased colonization in ducklings. These results suggest that LptD is involved in R. anatipestifer glutaraldehyde resistance and pathogenicity.
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Affiliation(s)
- Li Huang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Mingshu Wang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Ting Mo
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Mafeng Liu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | | | - Dekang Zhu
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Renyong Jia
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Shun Chen
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Xinxin Zhao
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Qiao Yang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Ying Wu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Shaqiu Zhang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Juan Huang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Bin Tian
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Yunya Liu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Ling Zhang
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Yanling Yu
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Leichang Pan
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Mujeeb Ur Rehman
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Xiaoyue Chen
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
| | - Anchun Cheng
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.,Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
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36
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Abstract
The outer membrane (OM) of Treponema pallidum, the uncultivatable agent of venereal syphilis, has long been the subject of misconceptions and controversy. Decades ago, researchers postulated that T. pallidum's poor surface antigenicity is the basis for its ability to cause persistent infection, but they mistakenly attributed this enigmatic property to the presence of a protective outer coat of serum proteins and mucopolysaccharides. Subsequent studies revealed that the OM is the barrier to antibody binding, that it contains a paucity of integral membrane proteins, and that the preponderance of the spirochete's immunogenic lipoproteins is periplasmic. Since the advent of recombinant DNA technology, the fragility of the OM, its low protein content, and the lack of sequence relatedness between T. pallidum and Gram-negative outer membrane proteins (OMPs) have complicated efforts to characterize molecules residing at the host-pathogen interface. We have overcome these hurdles using the genomic sequence in concert with computational tools to identify proteins predicted to form β-barrels, the hallmark conformation of OMPs in double-membrane organisms and evolutionarily related eukaryotic organelles. We also have employed diverse methodologies to confirm that some candidate OMPs do, in fact, form amphiphilic β-barrels and are surface-exposed in T. pallidum. These studies have led to a structural homology model for BamA and established the bipartite topology of the T. pallidum repeat (Tpr) family of proteins. Recent bioinformatics has identified several structural orthologs for well-characterized Gram-negative OMPs, suggesting that the T. pallidum OMP repertoire is more Gram-negative-like than previously supposed. Lipoprotein adhesins and proteases on the spirochete surface also may contribute to disease pathogenesis and protective immunity.
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Affiliation(s)
- Justin D Radolf
- Departments of Medicine, Pediatrics, Molecular Biology and Biophysics, Genetics and Genomic Sciences, and Immunology, UConn Health, Farmington, CT 06030-3715, USA.
| | - Sanjiv Kumar
- Department of Medicine, UConn Health, Farmington, CT 06030-3715, USA
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37
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Corradi V, Sejdiu BI, Mesa-Galloso H, Abdizadeh H, Noskov SY, Marrink SJ, Tieleman DP. Emerging Diversity in Lipid-Protein Interactions. Chem Rev 2019; 119:5775-5848. [PMID: 30758191 PMCID: PMC6509647 DOI: 10.1021/acs.chemrev.8b00451] [Citation(s) in RCA: 258] [Impact Index Per Article: 51.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Indexed: 02/07/2023]
Abstract
Membrane lipids interact with proteins in a variety of ways, ranging from providing a stable membrane environment for proteins to being embedded in to detailed roles in complicated and well-regulated protein functions. Experimental and computational advances are converging in a rapidly expanding research area of lipid-protein interactions. Experimentally, the database of high-resolution membrane protein structures is growing, as are capabilities to identify the complex lipid composition of different membranes, to probe the challenging time and length scales of lipid-protein interactions, and to link lipid-protein interactions to protein function in a variety of proteins. Computationally, more accurate membrane models and more powerful computers now enable a detailed look at lipid-protein interactions and increasing overlap with experimental observations for validation and joint interpretation of simulation and experiment. Here we review papers that use computational approaches to study detailed lipid-protein interactions, together with brief experimental and physiological contexts, aiming at comprehensive coverage of simulation papers in the last five years. Overall, a complex picture of lipid-protein interactions emerges, through a range of mechanisms including modulation of the physical properties of the lipid environment, detailed chemical interactions between lipids and proteins, and key functional roles of very specific lipids binding to well-defined binding sites on proteins. Computationally, despite important limitations, molecular dynamics simulations with current computer power and theoretical models are now in an excellent position to answer detailed questions about lipid-protein interactions.
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Affiliation(s)
- Valentina Corradi
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Besian I. Sejdiu
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Haydee Mesa-Galloso
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Haleh Abdizadeh
- Groningen
Biomolecular Sciences and Biotechnology Institute and Zernike Institute
for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Sergei Yu. Noskov
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Siewert J. Marrink
- Groningen
Biomolecular Sciences and Biotechnology Institute and Zernike Institute
for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - D. Peter Tieleman
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
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38
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Abstract
Gram-negative bacteria have an outer membrane that is positioned at the frontline of the cell's interaction with the environment and that serves as a barrier against noxious molecules including many antibiotics. This protective function mainly relies on lipopolysaccharide, a complex glycolipid located in the outer leaflet of the outer membrane. In this chapter we will first summarize lipopolysaccharide structure, functions and biosynthetic pathway and then we will discuss how it is transported and assembled to the cell surface. This is a remarkably complex process, as amphipathic lipopolysaccharide molecules must traverse three different cellular compartments to reach their final destination.
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39
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Huggins DJ, Biggin PC, Dämgen MA, Essex JW, Harris SA, Henchman RH, Khalid S, Kuzmanic A, Laughton CA, Michel J, Mulholland AJ, Rosta E, Sansom MSP, van der Kamp MW. Biomolecular simulations: From dynamics and mechanisms to computational assays of biological activity. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2018. [DOI: 10.1002/wcms.1393] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- David J. Huggins
- TCM Group, Cavendish Laboratory University of Cambridge Cambridge UK
- Unilever Centre, Department of Chemistry University of Cambridge Cambridge UK
- Department of Physiology and Biophysics Weill Cornell Medical College New York NY
| | | | - Marc A. Dämgen
- Department of Biochemistry University of Oxford Oxford UK
| | - Jonathan W. Essex
- School of Chemistry University of Southampton Southampton UK
- Institute for Life Sciences University of Southampton Southampton UK
| | - Sarah A. Harris
- School of Physics and Astronomy University of Leeds Leeds UK
- Astbury Centre for Structural and Molecular Biology University of Leeds Leeds UK
| | - Richard H. Henchman
- Manchester Institute of Biotechnology The University of Manchester Manchester UK
- School of Chemistry The University of Manchester Oxford UK
| | - Syma Khalid
- School of Chemistry University of Southampton Southampton UK
- Institute for Life Sciences University of Southampton Southampton UK
| | | | - Charles A. Laughton
- School of Pharmacy University of Nottingham Nottingham UK
- Centre for Biomolecular Sciences University of Nottingham Nottingham UK
| | - Julien Michel
- EaStCHEM school of Chemistry University of Edinburgh Edinburgh UK
| | - Adrian J. Mulholland
- Centre of Computational Chemistry, School of Chemistry University of Bristol Bristol UK
| | - Edina Rosta
- Department of Chemistry King's College London London UK
| | | | - Marc W. van der Kamp
- Centre of Computational Chemistry, School of Chemistry University of Bristol Bristol UK
- School of Biochemistry, Biomedical Sciences Building University of Bristol Bristol UK
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40
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Lin MH, Potel CM, Tehrani KHME, Heck AJR, Martin NI, Lemeer S. A New Tool to Reveal Bacterial Signaling Mechanisms in Antibiotic Treatment and Resistance. Mol Cell Proteomics 2018; 17:2496-2507. [PMID: 30232125 DOI: 10.1074/mcp.ra118.000880] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 09/12/2018] [Indexed: 11/06/2022] Open
Abstract
The rapid emergence of antimicrobial resistance is a major threat to human health. Antibiotics modulate a wide range of biological processes in bacteria and as such, the study of bacterial cellular signaling could aid the development of urgently needed new antibiotic agents. Due to the advances in bacterial phosphoproteomics, such a systemwide analysis of bacterial signaling in response to antibiotics has recently become feasible. Here we present a dynamic view of differential protein phosphorylation upon antibiotic treatment and antibiotic resistance. Most strikingly, differential phosphorylation was observed on highly conserved residues of resistance regulating transcription factors, implying a previously unanticipated role of phosphorylation mediated regulation. Using the comprehensive phosphoproteomics data presented here as a resource, future research can now focus on deciphering the precise signaling mechanisms contributing to resistance, eventually leading to alternative strategies to combat antimicrobial resistance.
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Affiliation(s)
- Miao-Hsia Lin
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research, University of Utrecht, Utrecht, The Netherlands; Netherlands Proteomics Center, University of Utrecht, Utrecht, The Netherlands
| | - Clement M Potel
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research, University of Utrecht, Utrecht, The Netherlands; Netherlands Proteomics Center, University of Utrecht, Utrecht, The Netherlands
| | - Kamaleddin H M E Tehrani
- Department of Chemical Biology & Drug Discovery, Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Utrecht, The Netherlands
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research, University of Utrecht, Utrecht, The Netherlands; Netherlands Proteomics Center, University of Utrecht, Utrecht, The Netherlands
| | - Nathaniel I Martin
- Department of Chemical Biology & Drug Discovery, Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Utrecht, The Netherlands
| | - Simone Lemeer
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research, University of Utrecht, Utrecht, The Netherlands; Netherlands Proteomics Center, University of Utrecht, Utrecht, The Netherlands.
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41
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Uddin MJ, Easwaran M, Ahn J. Characterization of bacteriophages specificity for antibiotic-resistant Salmonella typhimurium. ANN MICROBIOL 2018. [DOI: 10.1007/s13213-018-1370-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
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42
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Bertani BR, Taylor RJ, Nagy E, Kahne D, Ruiz N. A cluster of residues in the lipopolysaccharide exporter that selects substrate variants for transport to the outer membrane. Mol Microbiol 2018; 109:541-554. [PMID: 29995974 DOI: 10.1111/mmi.14059] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/16/2018] [Indexed: 01/03/2023]
Abstract
Most Gram-negative bacteria assemble lipopolysaccharides (LPS) on their surface to form a permeability barrier against many antimicrobials. LPS is synthesized at the inner membrane and then transported to the outer leaflet of the outer membrane. Although the overall LPS structure is conserved, LPS molecules can differ in composition at the species and strain level. Some bacteria also regulate when to modify phosphates on LPS at the inner membrane in order to become resistant to cationic antimicrobial peptides. The multi-protein Lpt trans-envelope machine, which transports LPS from the inner to the outer membrane, must therefore handle a variety of substrates. The most poorly understood step in LPS transport is how the ATP-binding cassette LptB2 FG transporter extracts LPS from the inner membrane. Here, we define residue K34 in LptG as a site within the structural cavity of the Escherichia coli LptB2 FG transporter that interacts electrostatically with phosphates on unmodified LPS. Alterations to this residue cause transport defects that are suppressed by the activation of the BasSR two-component signaling system, which results in modifications to the LPS phosphates. We also show this residue is part of a larger site in LptG that differentially contributes to the transport of unmodified and modified LPS.
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Affiliation(s)
- Blake R Bertani
- Department of Microbiology, The Ohio State University, Columbus, OH, 43210, USA
| | - Rebecca J Taylor
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Emma Nagy
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Daniel Kahne
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, 02138, USA.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA
| | - Natividad Ruiz
- Department of Microbiology, The Ohio State University, Columbus, OH, 43210, USA
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43
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Andolina G, Bencze LC, Zerbe K, Müller M, Steinmann J, Kocherla H, Mondal M, Sobek J, Moehle K, Malojčić G, Wollscheid B, Robinson JA. A Peptidomimetic Antibiotic Interacts with the Periplasmic Domain of LptD from Pseudomonas aeruginosa. ACS Chem Biol 2018; 13:666-675. [PMID: 29359918 DOI: 10.1021/acschembio.7b00822] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The outer membrane (OM) in Gram-negative bacteria is an asymmetric bilayer with mostly lipopolysaccharide (LPS) molecules in the outer leaflet. During OM biogenesis, new LPS molecules are transported from their site of assembly on the inner membrane to the OM by seven LPS transport proteins (LptA-G). The complex formed between the integral β-barrel OM protein LptD and the lipoprotein LptE is responsible for transporting LPS from the periplasmic side of the OM to its final location on the cell surface. Because of its essential function in many Gram-negative bacteria, the LPS transport pathway is an interesting target for the development of new antibiotics. A family of macrocyclic peptidomimetics was discovered recently that target LptD and inhibit LPS transport specifically in Pseudomonas spp. The related molecule Murepavadin is in clinical development for the treatment of life-threatening infections caused by P. aeruginosa. To characterize the interaction of these antibiotics with LptD from P. aeruginosa, we characterized the binding site by cross-linking to a photolabeling probe. We used a hypothesis-free mass spectrometry-based proteomic approach to provide evidence that the antibiotic cross-links to the periplasmic segment of LptD, containing a β-jellyroll domain and an N-terminal insert domain characteristic of Pseudomonas spp. Binding of the antibiotic to the periplasmic segment is expected to block LPS transport, consistent with the proposed mode of action and observed specificity of these antibiotics. These insights may prove valuable for the discovery of new antibiotics targeting the LPS transport pathway in other Gram-negative bacteria.
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Affiliation(s)
- Gloria Andolina
- Chemistry Department, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - László-Csaba Bencze
- Chemistry Department, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Katja Zerbe
- Chemistry Department, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Maik Müller
- Institute of Molecular Systems Biology, Department of Health Sciences and Technology, ETH Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, Switzerland
| | - Jessica Steinmann
- Chemistry Department, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Harsha Kocherla
- Chemistry Department, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Milon Mondal
- Chemistry Department, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Jens Sobek
- Functional Genomics Center Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Kerstin Moehle
- Chemistry Department, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Goran Malojčić
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Bernd Wollscheid
- Institute of Molecular Systems Biology, Department of Health Sciences and Technology, ETH Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, Switzerland
| | - John A. Robinson
- Chemistry Department, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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44
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Richie DL, Wang L, Chan H, De Pascale G, Six DA, Wei JR, Dean CR. A pathway-directed positive growth restoration assay to facilitate the discovery of lipid A and fatty acid biosynthesis inhibitors in Acinetobacter baumannii. PLoS One 2018; 13:e0193851. [PMID: 29505586 PMCID: PMC5837183 DOI: 10.1371/journal.pone.0193851] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Accepted: 02/19/2018] [Indexed: 11/19/2022] Open
Abstract
Acinetobacter baumannii ATCC 19606 can grow without lipooligosaccharide (LOS). Lack of LOS can result from disruption of the early lipid A biosynthetic pathway genes lpxA, lpxC or lpxD. Although LOS itself is not essential for growth of A. baumannii ATCC 19606, it was previously shown that depletion of the lipid A biosynthetic enzyme LpxK in cells inhibited growth due to the toxic accumulation of lipid A pathway intermediates. Growth of LpxK-depleted cells was restored by chemical inhibition of LOS biosynthesis using CHIR-090 (LpxC) and fatty acid biosynthesis using cerulenin (FabB/F) and pyridopyrimidine (acetyl-CoA-carboxylase). Here, we expand on this by showing that inhibition of enoyl-acyl carrier protein reductase (FabI), responsible for converting trans-2-enoyl-ACP into acyl-ACP during the fatty acid elongation cycle also restored growth during LpxK depletion. Inhibition of fatty acid biosynthesis during LpxK depletion rescued growth at 37°C, but not at 30°C, whereas rescue by LpxC inhibition was temperature independent. We exploited these observations to demonstrate proof of concept for a targeted medium-throughput growth restoration screening assay to identify small molecule inhibitors of LOS and fatty acid biosynthesis. The differential temperature dependence of fatty acid and LpxC inhibition provides a simple means by which to separate growth stimulating compounds by pathway. Targeted cell-based screening platforms such as this are important for faster identification of compounds inhibiting pathways of interest in antibacterial discovery for clinically relevant Gram-negative pathogens.
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Affiliation(s)
- Daryl L. Richie
- Novartis Institutes for BioMedical Research, Emeryville, CA, United States of America
| | - Lisha Wang
- Novartis Institutes for BioMedical Research, Emeryville, CA, United States of America
| | - Helen Chan
- Novartis Institutes for BioMedical Research, Emeryville, CA, United States of America
| | - Gianfranco De Pascale
- Novartis Institutes for BioMedical Research, Emeryville, CA, United States of America
| | - David A. Six
- Novartis Institutes for BioMedical Research, Emeryville, CA, United States of America
| | - Jun-Rong Wei
- Novartis Institutes for BioMedical Research, Emeryville, CA, United States of America
| | - Charles R. Dean
- Novartis Institutes for BioMedical Research, Emeryville, CA, United States of America
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45
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Schultz KM, Klug CS. Characterization of and lipopolysaccharide binding to the E. coli LptC protein dimer. Protein Sci 2018; 27:381-389. [PMID: 29024084 PMCID: PMC5775163 DOI: 10.1002/pro.3322] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 09/22/2017] [Accepted: 10/08/2017] [Indexed: 01/15/2023]
Abstract
Lipopolysaccharide (LPS, endotoxin) is the major component of the outer leaflet of the outer membrane of Gram-negative bacteria such as Escherichia coli and Salmonella typhimurium. LPS is a large lipid containing several acyl chains as its hydrophobic base and numerous sugars as its hydrophilic core and O-antigen domains, and is an essential element of the organisms' natural defenses in adverse environmental conditions. LptC is one of seven members of the lipopolysaccharide transport (Lpt) protein family that functions to transport LPS from the inner membrane (IM) to the outer leaflet of the outer membrane of the bacterium. LptC is anchored to the IM and associated with the IM LptFGB2 complex. It is hypothesized that LPS binds to LptC at the IM, transfers to LptA to cross the periplasm, and is inserted by LptDE into the outer leaflet of the outer membrane. The studies described here comprehensively characterize and quantitate the binding of LPS to LptC. Site-directed spin labeling electron paramagnetic resonance spectroscopy was utilized to characterize the LptC dimer in solution and monitor spin label mobility changes at 10 sites across the protein upon addition of exogenous LPS. The results indicate that soluble LptC forms concentration-independent N-terminal dimers in solution, LptA binding does not change the conformation of the LptC dimer nor appreciably disrupt the LptC dimer in vitro, and LPS binding affects the entire LptC protein, with the center and C-terminal regions showing a greater affinity for LPS than the N-terminal domain, which has similar dissociation constants to LptA.
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Affiliation(s)
- Kathryn M. Schultz
- Department of BiophysicsMedical College of WisconsinMilwaukeeWisconsin53226
| | - Candice S. Klug
- Department of BiophysicsMedical College of WisconsinMilwaukeeWisconsin53226
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46
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Nilsson I, Grove K, Dovala D, Uehara T, Lapointe G, Six DA. Molecular characterization and verification of azido-3,8-dideoxy-d- manno-oct-2-ulosonic acid incorporation into bacterial lipopolysaccharide. J Biol Chem 2017; 292:19840-19848. [PMID: 29018092 DOI: 10.1074/jbc.m117.814962] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 10/05/2017] [Indexed: 11/06/2022] Open
Abstract
3-Deoxy-d-manno-oct-2-ulosonic acid (Kdo) is an essential component of LPS in the outer leaflet of the Gram-negative bacterial outer membrane. Although labeling of Escherichia coli with the chemical reporter 8-azido-3,8-dideoxy-d-manno-oct-2-ulosonic acid (Kdo-N3) has been reported, its incorporation into LPS has not been directly shown. We have now verified Kdo-N3 incorporation into E. coli LPS at the molecular level. Using microscopy and PAGE analysis, we show that Kdo-N3 is localized to the outer membrane and specifically incorporates into rough and deep-rough LPS. In an E. coli strain lacking endogenous Kdo biosynthesis, supplementation with exogenous Kdo restored full-length core-LPS, which suggests that the Kdo biosynthetic pathways might not be essential in vivo in the presence of sufficient exogenous Kdo. In contrast, exogenous Kdo-N3 only restored a small fraction of core LPS with the majority incorporated into truncated LPS. The truncated LPS were identified as Kdo-N3-lipid IVA and (Kdo-N3)2-lipid IVA by MS analysis. The low level of Kdo-N3 incorporation could be partly explained by a 6-fold reduction in the specificity constant of the CMP-Kdo synthetase KdsB with Kdo-N3 compared with Kdo. These results indicate that the azido moiety in Kdo-N3 interferes with its utilization and may limit its utility as a tracer of LPS biosynthesis and transport in E. coli We propose that our findings will be helpful for researchers using Kdo and its chemical derivatives for investigating LPS biosynthesis, transport, and assembly in Gram-negative bacteria.
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Affiliation(s)
| | - Kerri Grove
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Emeryville, California 94608
| | | | | | - Guillaume Lapointe
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Emeryville, California 94608
| | - David A Six
- From the Departments of Infectious Diseases and
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47
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Sperandeo P, Martorana AM, Polissi A. The lipopolysaccharide transport (Lpt) machinery: A nonconventional transporter for lipopolysaccharide assembly at the outer membrane of Gram-negative bacteria. J Biol Chem 2017; 292:17981-17990. [PMID: 28878019 DOI: 10.1074/jbc.r117.802512] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The outer membrane (OM) of Gram-negative is a unique lipid bilayer containing LPS in its outer leaflet. Because of the presence of amphipathic LPS molecules, the OM behaves as an effective permeability barrier that makes Gram-negative bacteria inherently resistant to many antibiotics. This review focuses on LPS biogenesis and discusses recent advances that have contributed to our understanding of how this complex molecule is transported across the cellular envelope and is assembled at the OM outer leaflet. Clearly, this knowledge represents an important platform for the development of novel therapeutic options to manage Gram-negative infections.
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Affiliation(s)
- Paola Sperandeo
- From the Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, 20133 Milan and
| | - Alessandra M Martorana
- the Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, 20126 Milan, Italy
| | - Alessandra Polissi
- From the Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, 20133 Milan and
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Dong H, Tang X, Zhang Z, Dong C. Structural insight into lipopolysaccharide transport from the Gram-negative bacterial inner membrane to the outer membrane. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1461-1467. [PMID: 28821406 DOI: 10.1016/j.bbalip.2017.08.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/09/2017] [Accepted: 08/09/2017] [Indexed: 11/17/2022]
Abstract
Lipopolysaccharide (LPS) is an important component of the outer membrane (OM) of Gram-negative bacteria, playing essential roles in protecting bacteria from harsh environments, in drug resistance and in pathogenesis. LPS is synthesized in the cytoplasm and translocated to the periplasmic side of the inner membrane (IM), where it matures. Seven lipopolysaccharide transport proteins, LptA-G, form a trans‑envelope complex that is responsible for LPS extraction from the IM and transporting it across the periplasm to the OM. The LptD/E of the complex transports LPS across the OM and inserts it into the outer leaflet of the OM. In this review we focus upon structural and mechanistic studies of LPS transport proteins, with a particular focus upon the LPS ABC transporter LptB2FG. This ATP binding cassette transporter complex consists of twelve transmembrane segments and has a unique mechanism whereby it extracts LPS from the periplasmic face of the IM through a pair of lateral gates and then powers trans‑periplasmic transport to the OM through a slide formed by either of the periplasmic domains of LptF or LptG, LptC, LptA and the N-terminal domain of LptD. The structural and functional studies of the seven lipopolysaccharide transport proteins provide a platform to explore the unusual mechanisms of LPS extraction, transport and insertion from the inner membrane to the outer membrane. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop.
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Affiliation(s)
- Haohao Dong
- Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Xiaodi Tang
- Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Zhengyu Zhang
- Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Changjiang Dong
- Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
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Fantappiè L, Irene C, De Santis M, Armini A, Gagliardi A, Tomasi M, Parri M, Cafardi V, Bonomi S, Ganfini L, Zerbini F, Zanella I, Carnemolla C, Bini L, Grandi A, Grandi G. Some Gram-negative Lipoproteins Keep Their Surface Topology When Transplanted from One Species to Another and Deliver Foreign Polypeptides to the Bacterial Surface. Mol Cell Proteomics 2017; 16:1348-1364. [PMID: 28483926 PMCID: PMC5500766 DOI: 10.1074/mcp.m116.065094] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 05/05/2017] [Indexed: 11/29/2022] Open
Abstract
In Gram-negative bacteria, outer membrane-associated lipoproteins can either face the periplasm or protrude out of the bacterial surface. The mechanisms involved in lipoprotein transport through the outer membrane are not fully elucidated. Some lipoproteins reach the surface by using species-specific transport machinery. By contrast, a still poorly characterized group of lipoproteins appears to always cross the outer membrane, even when transplanted from one organism to another. To investigate such lipoproteins, we tested the expression and compartmentalization in E. coli of three surface-exposed lipoproteins, two from Neisseria meningitidis (Nm-fHbp and NHBA) and one from Aggregatibacter actinomycetemcomitans (Aa-fHbp). We found that all three lipoproteins were lipidated and compartmentalized in the E. coli outer membrane and in outer membrane vesicles. Furthermore, fluorescent antibody cell sorting analysis, proteolytic surface shaving, and confocal microscopy revealed that all three proteins were also exposed on the surface of the outer membrane. Removal or substitution of the first four amino acids following the lipidated cysteine residue and extensive deletions of the C-terminal regions in Nm-fHbp did not prevent the protein from reaching the surface of the outer membrane. Heterologous polypeptides, fused to the C termini of Nm-fHbp and NHBA, were efficiently transported to the E. coli cell surface and compartmentalized in outer membrane vesicles, demonstrating that these lipoproteins can be exploited in biotechnological applications requiring Gram-negative bacterial surface display of foreign polypeptides.
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Affiliation(s)
- Laura Fantappiè
- From the ‡Synthetic and Structural Vaccinology Unit, CIBIO, University of Trento, Via Sommarive, 9, 38123 Povo, Trento, Italy
| | - Carmela Irene
- From the ‡Synthetic and Structural Vaccinology Unit, CIBIO, University of Trento, Via Sommarive, 9, 38123 Povo, Trento, Italy
| | - Micaela De Santis
- From the ‡Synthetic and Structural Vaccinology Unit, CIBIO, University of Trento, Via Sommarive, 9, 38123 Povo, Trento, Italy
| | - Alessandro Armini
- §Functional Proteomics Lab., Department of Life Sciences, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Assunta Gagliardi
- §Functional Proteomics Lab., Department of Life Sciences, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Michele Tomasi
- From the ‡Synthetic and Structural Vaccinology Unit, CIBIO, University of Trento, Via Sommarive, 9, 38123 Povo, Trento, Italy
| | - Matteo Parri
- ¶Toscana Life Sciences Scientific Park, Via Fiorentina, 1 53100, Siena, Italy
| | - Valeria Cafardi
- From the ‡Synthetic and Structural Vaccinology Unit, CIBIO, University of Trento, Via Sommarive, 9, 38123 Povo, Trento, Italy
| | - Serena Bonomi
- From the ‡Synthetic and Structural Vaccinology Unit, CIBIO, University of Trento, Via Sommarive, 9, 38123 Povo, Trento, Italy
| | - Luisa Ganfini
- From the ‡Synthetic and Structural Vaccinology Unit, CIBIO, University of Trento, Via Sommarive, 9, 38123 Povo, Trento, Italy
| | - Francesca Zerbini
- From the ‡Synthetic and Structural Vaccinology Unit, CIBIO, University of Trento, Via Sommarive, 9, 38123 Povo, Trento, Italy
| | - Ilaria Zanella
- From the ‡Synthetic and Structural Vaccinology Unit, CIBIO, University of Trento, Via Sommarive, 9, 38123 Povo, Trento, Italy
| | - Chiara Carnemolla
- §Functional Proteomics Lab., Department of Life Sciences, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Luca Bini
- §Functional Proteomics Lab., Department of Life Sciences, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Alberto Grandi
- ¶Toscana Life Sciences Scientific Park, Via Fiorentina, 1 53100, Siena, Italy
| | - Guido Grandi
- From the ‡Synthetic and Structural Vaccinology Unit, CIBIO, University of Trento, Via Sommarive, 9, 38123 Povo, Trento, Italy;
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50
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Touchette MH, Seeliger JC. Transport of outer membrane lipids in mycobacteria. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1340-1354. [PMID: 28110100 DOI: 10.1016/j.bbalip.2017.01.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 01/13/2017] [Accepted: 01/13/2017] [Indexed: 12/24/2022]
Abstract
The complex organization of the mycobacterial cell wall poses unique challenges for the study of its assembly. Although mycobacteria are classified evolutionarily as Gram-positive bacteria, their cell wall architecture more closely resembles that of Gram-negative organisms. They possess not only an inner cytoplasmic membrane, but also a bilayer outer membrane that encloses an aqueous periplasm and includes diverse lipids that are required for the survival and virulence of pathogenic species. Questions surrounding how mycobacterial outer membrane lipids are transported from where they are made in the cytoplasm to where they function at the cell exterior are thus similar, and similarly compelling, to those that have driven the study of Gram-negative outer membrane transport pathways. However, little is understood about these processes in mycobacteria. Here we contextualize these questions by comparing our current knowledge of mycobacteria with better-defined systems in other organisms. Based on this analysis, we propose possible models and highlight continuing challenges to improving our understanding of outer membrane assembly in these medically and environmentally important bacteria. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop.
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Affiliation(s)
- Megan H Touchette
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, United States
| | - Jessica C Seeliger
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, United States.
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