1
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Bogdanov M. Exploring Uniform, Dual, and Dynamic Topologies of Membrane Proteins by Substituted Cysteine Accessibility Method (SCAM™). Methods Mol Biol 2024; 2715:121-157. [PMID: 37930526 PMCID: PMC10755806 DOI: 10.1007/978-1-0716-3445-5_9] [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] [Indexed: 11/07/2023]
Abstract
A described simple and advanced protocol for Substituted Cysteine Accessibility Method as applied to transmembrane (TM) orientation (SCAM™) permits a topology analysis of proteins in their native state and can be universally adapted to any membrane system to either systematically map an uniform or identify and quantify the degree of mixed topology or establish transmembrane assembly dynamics from relatively static experimental data such as endpoint topologies of membrane proteins. In this approach, noncritical individual amino acids that are thought to reside in the putative extracellular or intracellular loops of a membrane protein are replaced one at the time by cysteine residue, and the orientation with respect to the membrane is evaluated by using a pair of membrane-impermeable non-detectable and detectable thiol-reactive labeling reagents. For the most water-exposed cysteine residues in proteins, the thiol pKa lies in the range of 8-9, and formation of cysteinyl thiolate ions is optimum in aqueous rather in a nonpolar environment. These features and the ease of specific chemical modification with thiol reagents are central to SCAM™. Membrane side-specific sulfhydryl labeling allows to discriminate "exposed, protected or dynamic" cysteines strategically "implanted" at desired positions throughout cysteine less target protein template. The strategy described is widely used to map the topology of membrane protein and establish its transmembrane dynamics in intact cells of both diderm (two-membraned) Gram-negative and monoderm (one-membraned) Gram-positive bacteria, cell-derived oriented membrane vesicles, and proteoliposomes.
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Affiliation(s)
- Mikhail Bogdanov
- Department of Biochemistry & Molecular Biology, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, USA.
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2
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Smithers L, Degtjarik O, Weichert D, Huang CY, Boland C, Bowen K, Oluwole A, Lutomski C, Robinson CV, Scanlan EM, Wang M, Olieric V, Shalev-Benami M, Caffrey M. Structure snapshots reveal the mechanism of a bacterial membrane lipoprotein N-acyltransferase. SCIENCE ADVANCES 2023; 9:eadf5799. [PMID: 37390210 PMCID: PMC10313180 DOI: 10.1126/sciadv.adf5799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 05/26/2023] [Indexed: 07/02/2023]
Abstract
Bacterial lipoproteins (BLPs) decorate the surface of membranes in the cell envelope. They function in membrane assembly and stability, as enzymes, and in transport. The final enzyme in the BLP synthesis pathway is the apolipoprotein N-acyltransferase, Lnt, which is proposed to act by a ping-pong mechanism. Here, we use x-ray crystallography and cryo-electron microscopy to chart the structural changes undergone during the progress of the enzyme through the reaction. We identify a single active site that has evolved to bind, individually and sequentially, substrates that satisfy structural and chemical criteria to position reactive parts next to the catalytic triad for reaction. This study validates the ping-pong mechanism, explains the molecular bases for Lnt's substrate promiscuity, and should facilitate the design of antibiotics with minimal off-target effects.
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Affiliation(s)
- Luke Smithers
- School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin D02 R590, Ireland
| | - Oksana Degtjarik
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Dietmar Weichert
- School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin D02 R590, Ireland
| | - Chia-Ying Huang
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Coilín Boland
- School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin D02 R590, Ireland
| | - Katherine Bowen
- School of Chemistry, Trinity College Dublin, Dublin D02 R590, Ireland
| | - Abraham Oluwole
- Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Corinne Lutomski
- Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Carol V. Robinson
- Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Eoin M. Scanlan
- School of Chemistry, Trinity College Dublin, Dublin D02 R590, Ireland
| | - Meitian Wang
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Vincent Olieric
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Moran Shalev-Benami
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Martin Caffrey
- School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin D02 R590, Ireland
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3
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Zhou J, Cai Y, Liu Y, An H, Deng K, Ashraf MA, Zou L, Wang J. Breaking down the cell wall: Still an attractive antibacterial strategy. Front Microbiol 2022; 13:952633. [PMID: 36212892 PMCID: PMC9544107 DOI: 10.3389/fmicb.2022.952633] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 08/18/2022] [Indexed: 11/17/2022] Open
Abstract
Since the advent of penicillin, humans have known about and explored the phenomenon of bacterial inhibition via antibiotics. However, with changes in the global environment and the abuse of antibiotics, resistance mechanisms have been selected in bacteria, presenting huge threats and challenges to the global medical and health system. Thus, the study and development of new antimicrobials is of unprecedented urgency and difficulty. Bacteria surround themselves with a cell wall to maintain cell rigidity and protect against environmental insults. Humans have taken advantage of antibiotics to target the bacterial cell wall, yielding some of the most widely used antibiotics to date. The cell wall is essential for bacterial growth and virulence but is absent from humans, remaining a high-priority target for antibiotic screening throughout the antibiotic era. Here, we review the extensively studied targets, i.e., MurA, MurB, MurC, MurD, MurE, MurF, Alr, Ddl, MurI, MurG, lipid A, and BamA in the cell wall, starting from the very beginning to the latest developments to elucidate antimicrobial screening. Furthermore, recent advances, including MraY and MsbA in peptidoglycan and lipopolysaccharide, and tagO, LtaS, LspA, Lgt, Lnt, Tol-Pal, MntC, and OspA in teichoic acid and lipoprotein, have also been profoundly discussed. The review further highlights that the application of new methods such as macromolecular labeling, compound libraries construction, and structure-based drug design will inspire researchers to screen ideal antibiotics.
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Affiliation(s)
- Jingxuan Zhou
- The People’s Hospital of China Three Gorges University, Yichang, Hubei, China
- Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
- The Institute of Infection and Inflammation, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
| | - Yi Cai
- Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
- The Institute of Infection and Inflammation, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
| | - Ying Liu
- Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
- The Institute of Infection and Inflammation, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
| | - Haoyue An
- Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
- The Institute of Infection and Inflammation, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
| | - Kaihong Deng
- Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
- The Institute of Infection and Inflammation, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
| | - Muhammad Awais Ashraf
- Department of Microbiology, Government College University Faisalabad, Faisalabad, Pakistan
| | - Lili Zou
- Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
- The Institute of Infection and Inflammation, College of Basic Medical Sciences, China Three Gorges University, Yichang, Hubei, China
| | - Jun Wang
- The People’s Hospital of China Three Gorges University, Yichang, Hubei, China
- *Correspondence: Jun Wang,
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4
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Legood S, Boneca IG, Buddelmeijer N. Mode of action of lipoprotein modification enzymes-Novel antibacterial targets. Mol Microbiol 2021; 115:356-365. [PMID: 32979868 PMCID: PMC8048626 DOI: 10.1111/mmi.14610] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 09/10/2020] [Indexed: 01/04/2023]
Abstract
Lipoproteins are characterized by a fatty acid moiety at their amino-terminus through which they are anchored into membranes. They fulfill a variety of essential functions in bacterial cells, such as cell wall maintenance, virulence, efflux of toxic elements including antibiotics, and uptake of nutrients. The posttranslational modification process of lipoproteins involves the sequential action of integral membrane enzymes and phospholipids as acyl donors. In recent years, the structures of the lipoprotein modification enzymes have been solved by X-ray crystallography leading to a greater insight into their function and the molecular mechanism of the reactions. The catalytic domains of the enzymes are exposed to the periplasm or external milieu and are readily accessible to small molecules. Since the lipoprotein modification pathway is essential in proteobacteria, it is a potential target for the development of novel antibiotics. In this review, we discuss recent literature on the structural characterization of the enzymes, and the in vitro activity assays compatible with high-throughput screening for inhibitors, with perspectives on the development of new antimicrobial agents.
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Affiliation(s)
- Simon Legood
- Institut PasteurUnité Biologie et Génétique de la Paroi BactérienneParisFrance
- CNRS, UMR 2001 « Microbiologie intégrative et Moléculaire »ParisFrance
- INSERM Groupe AvenirParisFrance
- Université de ParisSorbonne Paris CitéParisFrance
| | - Ivo G. Boneca
- Institut PasteurUnité Biologie et Génétique de la Paroi BactérienneParisFrance
- CNRS, UMR 2001 « Microbiologie intégrative et Moléculaire »ParisFrance
- INSERM Groupe AvenirParisFrance
| | - Nienke Buddelmeijer
- Institut PasteurUnité Biologie et Génétique de la Paroi BactérienneParisFrance
- CNRS, UMR 2001 « Microbiologie intégrative et Moléculaire »ParisFrance
- INSERM Groupe AvenirParisFrance
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5
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Icke C, Hodges FJ, Pullela K, McKeand SA, Bryant JA, Cunningham AF, Cole JA, Henderson IR. Glycine acylation and trafficking of a new class of bacterial lipoprotein by a composite secretion system. eLife 2021; 10:63762. [PMID: 33625358 PMCID: PMC7943197 DOI: 10.7554/elife.63762] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 02/23/2021] [Indexed: 01/21/2023] Open
Abstract
Protein acylation is critical for many cellular functions across all domains of life. In bacteria, lipoproteins have important roles in virulence and are targets for the development of antimicrobials and vaccines. Bacterial lipoproteins are secreted from the cytosol via the Sec pathway and acylated on an N-terminal cysteine residue through the action of three enzymes. In Gram-negative bacteria, the Lol pathway transports lipoproteins to the outer membrane. Here, we demonstrate that the Aat secretion system is a composite system sharing similarity with elements of a type I secretion systems and the Lol pathway. During secretion, the AatD subunit acylates the substrate CexE on a highly conserved N-terminal glycine residue. Mutations disrupting glycine acylation interfere with membrane incorporation and trafficking. Our data reveal CexE as the first member of a new class of glycine-acylated lipoprotein, while Aat represents a new secretion system that displays the substrate lipoprotein on the cell surface.
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Affiliation(s)
- Christopher Icke
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Freya J Hodges
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Karthik Pullela
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | | | | | - Adam F Cunningham
- Institute of Microbiology and Infection, Birmingham, United Kingdom.,Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, United Kingdom
| | - Jeff A Cole
- Institute of Microbiology and Infection, Birmingham, United Kingdom
| | - Ian R Henderson
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
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6
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Armbruster KM, Komazin G, Meredith TC. Bacterial lyso-form lipoproteins are synthesized via an intramolecular acyl chain migration. J Biol Chem 2020; 295:10195-10211. [PMID: 32471867 DOI: 10.1074/jbc.ra120.014000] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 05/22/2020] [Indexed: 01/08/2023] Open
Abstract
All bacterial lipoproteins share a variably acylated N-terminal cysteine residue. Gram-negative bacterial lipoproteins are triacylated with a thioether-linked diacylglycerol moiety and an N-acyl chain. The latter is transferred from a membrane phospholipid donor to the α-amino terminus by the enzyme lipoprotein N-acyltransferase (Lnt), using an active-site cysteine thioester covalent intermediate. Many Gram-positive Firmicutes also have N-acylated lipoproteins, but the enzymes catalyzing N-acylation remain uncharacterized. The integral membrane protein Lit (lipoprotein intramolecular transacylase) from the opportunistic nosocomial pathogen Enterococcus faecalis synthesizes a specific lysoform lipoprotein (N-acyl S-monoacylglycerol) chemotype by an unknown mechanism that helps this bacterium evade immune recognition by the Toll-like receptor 2 family complex. Here, we used a deuterium-labeled lipoprotein substrate with reconstituted Lit to investigate intramolecular acyl chain transfer. We observed that Lit transfers the sn-2 ester-linked lipid from the diacylglycerol moiety to the α-amino terminus without forming a covalent thioester intermediate. Utilizing Mut-Seq to analyze an alanine scan library of Lit alleles, we identified two stretches of functionally important amino acid residues containing two conserved histidines. Topology maps based on reporter fusion assays and cysteine accessibility placed both histidines in the extracellular half of the cytoplasmic membrane. We propose a general acid base-promoted catalytic mechanism, invoking direct nucleophilic attack by the substrate α-amino group on the sn-2 ester to form a cyclic tetrahedral intermediate that then collapses to produce lyso-lipoprotein. Lit is a unique example of an intramolecular transacylase differentiated from that catalyzed by Lnt, and provides insight into the heterogeneity of bacterial lipoprotein biosynthetic systems.
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Affiliation(s)
- Krista M Armbruster
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Gloria Komazin
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Timothy C Meredith
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA .,The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park Pennsylvania, USA
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7
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Xia J, Feng B, Wen G, Xue W, Ma G, Zhang H, Wu S. Bacterial Lipoprotein Biosynthetic Pathway as a Potential Target for Structure-based Design of Antibacterial Agents. Curr Med Chem 2020; 27:1132-1150. [PMID: 30360704 DOI: 10.2174/0929867325666181008143411] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 07/31/2018] [Accepted: 08/15/2018] [Indexed: 12/20/2022]
Abstract
BACKGROUND Antibiotic resistance is currently a serious problem for global public health. To this end, discovery of new antibacterial drugs that interact with novel targets is important. The biosynthesis of lipoproteins is vital to bacterial survival and its inhibitors have shown efficacy against a range of bacteria, thus bacterial lipoprotein biosynthetic pathway is a potential target. METHODS At first, the literature that covered the basic concept of bacterial lipoprotein biosynthetic pathway as well as biochemical characterization of three key enzymes was reviewed. Then, the recently resolved crystal structures of the three enzymes were retrieved from Protein Data Bank (PDB) and the essential residues in the active sites were analyzed. Lastly, all the available specific inhibitors targeting this pathway and their Structure-activity Relationship (SAR) were discussed. RESULTS We briefly introduce the bacterial lipoprotein biosynthetic pathway and describe the structures and functions of three key enzymes in detail. In addition, we present much knowledge on ligand recognition that may facilitate structure-based drug design. Moreover, we focus on the SAR of LspA inhibitors and discuss their potency and drug-likeness. CONCLUSION This review presents a clear background of lipoprotein biosynthetic pathway and provides practical clues for structure-based drug design. In particular, the most up-to-date knowledge on the SAR of lead compounds targeting this pathway would be a good reference for discovery of a novel class of antibacterial agents.
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Affiliation(s)
- Jie Xia
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Department of New Drug Research and Development, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
| | - Bo Feng
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Department of New Drug Research and Development, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
| | - Gang Wen
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Department of New Drug Research and Development, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
| | - Wenjie Xue
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Department of New Drug Research and Development, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
| | - Guixing Ma
- Department of Biology, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment and SUSTech-HKU joint laboratories for matrix biology, Southern University of Science and Technology, Shenzhen 518055, China
| | - Hongmin Zhang
- Department of Biology, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment and SUSTech-HKU joint laboratories for matrix biology, Southern University of Science and Technology, Shenzhen 518055, China
| | - Song Wu
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Department of New Drug Research and Development, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
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8
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Conformational changes in Apolipoprotein N-acyltransferase (Lnt). Sci Rep 2020; 10:639. [PMID: 31959792 PMCID: PMC6971011 DOI: 10.1038/s41598-020-57419-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 12/31/2019] [Indexed: 11/10/2022] Open
Abstract
Lipoproteins are important components of the cell envelope and are responsible for many essential cellular functions. They are produced by the post-translational covalent attachment of lipids that occurs via a sequential 3-step process controlled by three integral membrane enzymes. The last step of this process, unique to Gram-negative bacteria, is the N-acylation of the terminal cysteine by Apolipoprotein N-acyltransferase (Lnt) to form the final mature lipoprotein. Here we report 2 crystal forms of Lnt from Escherichia coli. In one form we observe a highly dynamic arm that is able to restrict access to the active site as well as a covalent modification to the active site cysteine consistent with the thioester acyl-intermediate. In the second form, the enzyme crystallized in an open conformation exposing the active site to the environment. In total we observe 3 unique Lnt molecules that when taken together suggest the movement of essential loops and residues are triggered by substrate binding that could control the interaction between Lnt and the incoming substrate apolipoprotein. The results provide a dynamic context for residues shown to be central for Lnt function and provide further insights into its mechanism.
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9
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A sensitive fluorescence-based assay to monitor enzymatic activity of the essential integral membrane protein Apolipoprotein N-acyltransferase (Lnt). Sci Rep 2019; 9:15978. [PMID: 31685855 PMCID: PMC6828757 DOI: 10.1038/s41598-019-52106-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 10/08/2019] [Indexed: 12/20/2022] Open
Abstract
Lipoprotein modification is an essential process in Gram-negative bacteria. The action of three integral membrane proteins that catalyze the transfer of fatty acids derived from membrane phospholipids or cleave the signal peptide of the lipoprotein substrate result in the formation of mature triacylated proteins. Inactivation of the enzymes leads to mis-localization of immature lipoproteins and consequently cell death. Biochemical studies and the development of in vitro assays are challenging due to the fact that the enzymes and substrates are all membrane-embedded proteins difficult to overproduce and purify. Here we describe a sensitive fluorescence-based assay to monitor bacterial apolipoprotein N-acyltransferase activity.
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10
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El Arnaout T, Soulimane T. Targeting Lipoprotein Biogenesis: Considerations towards Antimicrobials. Trends Biochem Sci 2019; 44:701-715. [PMID: 31036406 DOI: 10.1016/j.tibs.2019.03.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 03/14/2019] [Accepted: 03/25/2019] [Indexed: 12/25/2022]
Abstract
Decades have passed without approval of a new antibiotic class. Several companies have recently halted related discovery efforts because of multiple obstacles. One promising route under research is to target the lipoprotein maturation pathway in light of major recent findings and the virulence roles of lipoproteins. To support the future design of selective drugs, considerations and priority-setting are established for the main lipoprotein processing enzymes (Lgt, LspA, and Lnt) based on microbiology, biochemistry, structural biology, chemical design, and pharmacology. Although not all bacterial species will be similarly impacted by drug candidates, several advantages make LspA a top target to pursue in the development of novel antibiotics effective against bacteria that are resistant to existing drugs.
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Affiliation(s)
- Toufic El Arnaout
- Kappa Crystals Ltd, Dublin, Ireland; School of Food Science and Environmental Health, Technological University (TU) Dublin City Campus, TU, Dublin, Dublin, Ireland.
| | - Tewfik Soulimane
- Bernal Institute, University of Limerick, Limerick, V94 T9PX, Ireland; Department of Chemical Sciences, University of Limerick, Limerick, V94 T9PX, Ireland
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11
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Lin Y, Deepak RNVK, Zheng JZ, Fan H, Zheng L. A dual substrate-accessing mechanism of a major facilitator superfamily protein facilitates lysophospholipid flipping across the cell membrane. J Biol Chem 2018; 293:19919-19931. [PMID: 30373772 DOI: 10.1074/jbc.ra118.005548] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 10/23/2018] [Indexed: 11/06/2022] Open
Abstract
Lysophospholipid transporter (LplT) is a member of the major facilitator superfamily present in many Gram-negative bacteria. LplT catalyzes flipping of lysophospholipids (LPLs) across the bacterial inner membrane, playing an important role in bacterial membrane homeostasis. We previously reported that LplT promotes both uptake of exogenous LPLs and intramembranous LPL flipping across the bilayer. To gain mechanistic insight into this dual LPL-flipping activity, here we implemented a combination of computational approaches and LPL transport analyses to study LPL binding of and translocation by LplT. Our results suggest that LplT translocates LPLs through an elongated cavity exhibiting an extremely asymmetric polarity. We found that two D(E)N motifs form a head group-binding site, in which the carboxylate group of Asp-30 is important for LPL head group recognition. Substitutions of residues in the head group-binding site disrupted both LPL uptake and flipping activities. However, alteration of hydrophobic residues on the interface between the N- and C-terminal domains impaired LPL flipping specifically, resulting in LPLs accumulation in the membrane, but LPL uptake remained active. These results suggest a dual substrate-accessing mechanism, in which LplT recruits LPLs to its substrate-binding site via two routes, either from its extracellular entry or through a membrane-embedded groove between transmembrane helices, and then moves them toward the inner membrane leaflet. This LPL-flipping mechanism is likely conserved in many bacterial species, and our findings illustrate how LplT adjusts the major facilitator superfamily translocation pathway to perform its versatile lipid homeostatic functions.
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Affiliation(s)
- Yibin Lin
- From the Department of Biochemistry and Molecular Biology, Center for Membrane Biology, the University of Texas Health Science Center at Houston McGovern Medical School, Houston Texas 77030
| | - R N V Krishna Deepak
- the Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), 138671 Singapore, and
| | - Jonathan Zixiang Zheng
- From the Department of Biochemistry and Molecular Biology, Center for Membrane Biology, the University of Texas Health Science Center at Houston McGovern Medical School, Houston Texas 77030
| | - Hao Fan
- the Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), 138671 Singapore, and .,the Department of Biological Sciences (DBS), National University of Singapore, 117558 Singapore, and Center for Computational Biology, DUKE-NUS Medical School, 169857 Singapore
| | - Lei Zheng
- From the Department of Biochemistry and Molecular Biology, Center for Membrane Biology, the University of Texas Health Science Center at Houston McGovern Medical School, Houston Texas 77030,
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12
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Gwin CM, Prakash N, Christian Belisario J, Haider L, Rosen ML, Martinez LR, Rigel NW. The apolipoprotein N-acyl transferase Lnt is dispensable for growth in Acinetobacter species. MICROBIOLOGY-SGM 2018; 164:1547-1556. [PMID: 30307391 DOI: 10.1099/mic.0.000726] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Directing the flow of protein traffic is a critical task faced by all cellular organisms. In Gram-negative bacteria, this traffic includes lipoproteins. Lipoproteins are synthesized as precursors in the cytoplasm and receive their acyl modifications upon export across the inner membrane. The third and final acyl chain is added by Lnt, which until recently was thought to be essential in all Gram-negatives. In this report, we show that Acinetobacter species can also tolerate a complete loss-of-function mutation in lnt. Absence of a fully functional Lnt impairs modification of lipoproteins, increases outer membrane permeability and susceptibility to antibiotics, and alters normal cellular morphology. In addition, we show that loss of lnt triggers a global transcriptional response to this added cellular stress. Taken together, our findings provide new insights on and support the growing revisions to the Gram-negative lipoprotein biogenesis paradigm.
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Affiliation(s)
- Celena M Gwin
- 1Department of Biology, Hofstra University, Hempstead, NY, USA.,2Department of Microbial Pathogenesis, Yale University, New Haven, CT, USA
| | - Natalia Prakash
- 1Department of Biology, Hofstra University, Hempstead, NY, USA
| | - J Christian Belisario
- 3Department of Biomedical Sciences, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY, USA
| | - Lubaina Haider
- 1Department of Biology, Hofstra University, Hempstead, NY, USA.,4College of Medicine, SUNY-Downstate Medical Center, Brooklyn, NY, USA
| | - Marlene L Rosen
- 1Department of Biology, Hofstra University, Hempstead, NY, USA
| | - Luis R Martinez
- 3Department of Biomedical Sciences, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY, USA.,5Department of Biological Sciences, The Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, USA
| | - Nathan W Rigel
- 1Department of Biology, Hofstra University, Hempstead, NY, USA
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13
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Cheng W, Doyle DA, El Arnaout T. The N-acyltransferase Lnt: Structure-function insights from recent simultaneous studies. Int J Biol Macromol 2018; 117:870-877. [PMID: 29859843 DOI: 10.1016/j.ijbiomac.2018.05.229] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 05/29/2018] [Accepted: 05/30/2018] [Indexed: 02/05/2023]
Abstract
Bacterial lipoproteins have been researched for decades due to their roles in a large number of biological functions. There were no structures of their main three membrane processing enzymes, until 2016 for Lgt and LspA, and then 2017 for Lnt with not one but three simultaneous, independent publications. We have analyzed the recent findings for this apolipoprotein N-acyltransferase Lnt, with comparisons between the novel structures, and with soluble nitrilases, to determine the significance of unique features in terms of substrate's recognition and binding mechanism influenced by exclusive residues, two transmembrane helices, and a flexible loop.
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Affiliation(s)
- Wei Cheng
- Division of Respiratory and Critical Care Medicine, State Key Laboratory of Biotherapy, West China Hospital of Sichuan University and Collaborative Innovation Center of Biotherapy, Chengdu, Sichuan 610041, China
| | - Declan A Doyle
- Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK
| | - Toufic El Arnaout
- School of Food Science and Environmental Health, Dublin Institute of Technology, Marlborough St, Dublin 1, Ireland.
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14
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Biophysical characterization and stabilization of detergent-solubilized lipoprotein N-acyl transferase from P. aeruginosa and E. coli. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1384-1393. [PMID: 29573991 DOI: 10.1016/j.bbamem.2018.03.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 03/18/2018] [Accepted: 03/20/2018] [Indexed: 11/23/2022]
Abstract
Lipoproteins are important for bacterial growth and virulence and interest in them as targets for antibiotic development is growing. Lipoprotein N-acyl transferase (Lnt) catalyzes the final step in the lipoprotein posttranslational processing pathway. The mature lipoprotein can remain in the inner membrane or be trafficked to the outer membrane in the case of diderm prokaryotes. With a view to obtaining high-resolution crystal structures of membrane integral Lnt for use in drug discovery a program was undertaken to generate milligram quantities of stable, homogenous and functional protein. This involved screening across bacterial species for suitable orthologues and optimization at the level of protein expression, solubilization and stability. Combining biophysical and functional characterization, orthologous Lnt from Escherichia coli and the opportunistic human pathogen Pseudomonas aeruginosa was identified as suitable for the proposed structure determination campaign that ultimately yielded crystal structures. The rational approaches taken that eventually provided structure-quality protein are presented in this report.
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15
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Nguyen MT, Uebele J, Kumari N, Nakayama H, Peter L, Ticha O, Woischnig AK, Schmaler M, Khanna N, Dohmae N, Lee BL, Bekeredjian-Ding I, Götz F. Lipid moieties on lipoproteins of commensal and non-commensal staphylococci induce differential immune responses. Nat Commun 2017; 8:2246. [PMID: 29269769 PMCID: PMC5740139 DOI: 10.1038/s41467-017-02234-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 11/15/2017] [Indexed: 02/08/2023] Open
Abstract
Lipoproteins (Lpp) of Gram-positive bacteria are major players in alerting our immune system. Here, we show that the TLR2 response induced by commensal species Staphylococcus aureus and Staphylococcus epidermidis is almost ten times lower than that induced by noncommensal Staphylococcus carnosus, and this is at least partially due to their different modifications of the Lpp lipid moieties. The N terminus of the lipid moiety is acylated with a long-chain fatty acid (C17) in S. aureus and S. epidermidis, while it is acylated with a short-chain fatty acid (C2) in S. carnosus. The long-chain N-acylated Lpp, recognized by TLR2-TLR1 receptors, silences innate and adaptive immune responses, while the short-chain N-acetylated Lpp, recognized by TLR2-TLR6 receptors, boosts it.
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Affiliation(s)
- Minh-Thu Nguyen
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, 72076, Germany.,School of Biological and Food Technology, Hanoi University of Science and Technology, Hanoi, 1000, Vietnam
| | - Julia Uebele
- Paul-Ehrlich-Institute, Federal Regulatory Agency for Vaccines and Biomedicines, Langen, 63225, Germany
| | - Nimerta Kumari
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, 72076, Germany
| | - Hiroshi Nakayama
- Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, Saitama, 351-0198, Japan
| | - Lena Peter
- Paul-Ehrlich-Institute, Federal Regulatory Agency for Vaccines and Biomedicines, Langen, 63225, Germany
| | - Olga Ticha
- Paul-Ehrlich-Institute, Federal Regulatory Agency for Vaccines and Biomedicines, Langen, 63225, Germany
| | - Anne-Kathrin Woischnig
- Laboratory of Infection Biology, Department of Biomedicine, University Hospital Basel, Basel, CH-4031, Switzerland
| | - Mathias Schmaler
- Laboratory of Infection Biology, Department of Biomedicine, University Hospital Basel, Basel, CH-4031, Switzerland
| | - Nina Khanna
- Laboratory of Infection Biology, Department of Biomedicine, University Hospital Basel, Basel, CH-4031, Switzerland
| | - Naoshi Dohmae
- Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, Saitama, 351-0198, Japan
| | - Bok Luel Lee
- National Research Laboratory of Defense Proteins, College of Pharmacy, Pusan National University, Pusan, 609-735, South Korea
| | - Isabelle Bekeredjian-Ding
- Paul-Ehrlich-Institute, Federal Regulatory Agency for Vaccines and Biomedicines, Langen, 63225, Germany
| | - Friedrich Götz
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, 72076, Germany.
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16
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Structural insights into lipoprotein N-acylation by Escherichia coli apolipoprotein N-acyltransferase. Proc Natl Acad Sci U S A 2017; 114:E6044-E6053. [PMID: 28698362 DOI: 10.1073/pnas.1707813114] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Gram-negative bacteria express a diverse array of lipoproteins that are essential for various aspects of cell growth and virulence, including nutrient uptake, signal transduction, adhesion, conjugation, sporulation, and outer membrane protein folding. Lipoprotein maturation requires the sequential activity of three enzymes that are embedded in the cytoplasmic membrane. First, phosphatidylglycerol:prolipoprotein diacylglyceryl transferase (Lgt) recognizes a conserved lipobox motif within the prolipoprotein signal sequence and catalyzes the addition of diacylglycerol to an invariant cysteine. The signal sequence is then cleaved by signal peptidase II (LspA) to give an N-terminal S-diacylglyceryl cysteine. Finally, apolipoprotein N-acyltransferase (Lnt) catalyzes the transfer of the sn-1-acyl chain of phosphatidylethanolamine to this N-terminal cysteine, generating a mature, triacylated lipoprotein. Although structural studies of Lgt and LspA have yielded significant mechanistic insights into this essential biosynthetic pathway, the structure of Lnt has remained elusive. Here, we present crystal structures of wild-type and an active-site mutant of Escherichia coli Lnt. The structures reveal a monomeric eight-transmembrane helix fold that supports a periplasmic carbon-nitrogen hydrolase domain containing a Cys-Glu-Lys catalytic triad. Two lipids are bound at the active site in the structures, and we propose a putative phosphate recognition site where a chloride ion is coordinated near the active site. Based on these structures and complementary cell-based, biochemical, and molecular dynamics approaches, we propose a mechanism for substrate engagement and catalysis by E. coli Lnt.
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17
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Lu G, Xu Y, Zhang K, Xiong Y, Li H, Cui L, Wang X, Lou J, Zhai Y, Sun F, Zhang XC. Crystal structure of E. coli apolipoprotein N-acyl transferase. Nat Commun 2017; 8:15948. [PMID: 28885614 PMCID: PMC5500890 DOI: 10.1038/ncomms15948] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 05/13/2017] [Indexed: 11/09/2022] Open
Abstract
In Gram-negative bacteria, lipid modification of proteins is catalysed in a three-step pathway. Apolipoprotein N-acyl transferase (Lnt) catalyses the third step in this pathway, whereby it transfers an acyl chain from a phospholipid to the amine group of the N-terminal cysteine residue of the apolipoprotein. Here, we report the 2.6-Å crystal structure of Escherichia coli Lnt. This enzyme contains an exo-membrane nitrilase domain fused to a transmembrane (TM) domain. The TM domain of Lnt contains eight TM helices which form a membrane-embedded cavity with a lateral opening and a periplasmic exit. The nitrilase domain is located on the periplasmic side of the membrane, with its catalytic cavity connected to the periplasmic exit of the TM domain. An amphipathic lid loop from the nitrilase domain interacts with the periplasmic lipid leaflet, forming an interfacial entrance from the lipid bilayer to the catalytic centre for both the lipid donor and acceptor substrates.
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Affiliation(s)
- Guangyuan Lu
- National Laboratory of Macromolecules, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.,School of Life Sciences, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
| | - Yingzhi Xu
- National Laboratory of Macromolecules, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Kai Zhang
- National Laboratory of Macromolecules, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Yong Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06411, USA
| | - He Li
- National Laboratory of Macromolecules, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Lei Cui
- National Laboratory of Macromolecules, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Xianping Wang
- National Laboratory of Macromolecules, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.,School of Life Sciences, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
| | - Jizhong Lou
- National Laboratory of Macromolecules, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.,School of Life Sciences, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
| | - Yujia Zhai
- National Laboratory of Macromolecules, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Fei Sun
- National Laboratory of Macromolecules, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.,School of Life Sciences, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
| | - Xuejun C Zhang
- National Laboratory of Macromolecules, Institute of Biophysics, CAS Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.,School of Life Sciences, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China
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18
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Structural insights into the mechanism of the membrane integral N-acyltransferase step in bacterial lipoprotein synthesis. Nat Commun 2017; 8:15952. [PMID: 28675161 PMCID: PMC5500888 DOI: 10.1038/ncomms15952] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 05/13/2017] [Indexed: 02/07/2023] Open
Abstract
Lipoproteins serve essential roles in the bacterial cell envelope. The posttranslational modification pathway leading to lipoprotein synthesis involves three enzymes. All are potential targets for the development of new antibiotics. Here we report the crystal structure of the last enzyme in the pathway, apolipoprotein N-acyltransferase, Lnt, responsible for adding a third acyl chain to the lipoprotein’s invariant diacylated N-terminal cysteine. Structures of Lnt from Pseudomonas aeruginosa and Escherichia coli have been solved; they are remarkably similar. Both consist of a membrane domain on which sits a globular periplasmic domain. The active site resides above the membrane interface where the domains meet facing into the periplasm. The structures are consistent with the proposed ping-pong reaction mechanism and suggest plausible routes by which substrates and products enter and leave the active site. While Lnt may present challenges for antibiotic development, the structures described should facilitate design of therapeutics with reduced off-target effects. Lipoproteins are essential components of bacterial membranes. Here the authors present the crystal structures of Pseudomonas aeruginosa and Escherichia coli apolipoprotein N-acyltransferase, which catalyses the final step in the lipoprotein synthesis pathway, and give insights into its mechanism.
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19
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Identification of the Lyso-Form N-Acyl Intramolecular Transferase in Low-GC Firmicutes. J Bacteriol 2017; 199:JB.00099-17. [PMID: 28320885 DOI: 10.1128/jb.00099-17] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 03/14/2017] [Indexed: 12/25/2022] Open
Abstract
Bacterial lipoproteins are embedded in the cell membrane of both Gram-positive and Gram-negative bacteria, where they serve numerous functions central to cell envelope physiology. Lipoproteins are tethered to the membrane by an N-acyl-S-(mono/di)-acyl-glyceryl-cysteine anchor that is variously acylated depending on the genus. In several low-GC, Gram-positive firmicutes, a monoacyl-glyceryl-cysteine with an N-terminal fatty acid (known as the lyso form) has been reported, though how it is formed is unknown. Here, through an intergenic complementation rescue assay in Escherichia coli, we report the identification of a common orthologous transmembrane protein in both Enterococcus faecalis and Bacillus cereus that is capable of forming lyso-form lipoproteins. When deleted from the native host, lipoproteins remain diacylated with a free N terminus, as maturation to the N-acylated lyso form is abolished. Evidence is presented suggesting that the previously unknown gene product functions through a novel intramolecular transacylation mechanism, transferring a fatty acid from the diacylglycerol moiety to the α-amino group of the lipidated cysteine. As such, the discovered gene has been named lipoprotein intramolecular transacylase (lit), to differentiate it from the gene for the intermolecular N-acyltransferase (lnt) involved in triacyl lipoprotein biosynthesis in Gram-negative organisms.IMPORTANCE This study identifies a new enzyme, conserved among low-GC, Gram-positive bacteria, that is involved in bacterial lipoprotein biosynthesis and synthesizes lyso-form lipoproteins. Its discovery is an essential first step in determining the physiological role of N-terminal lipoprotein acylation in Gram-positive bacteria and how these modifications impact bacterial cell envelope function.
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20
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Bogdanov M. Mapping of Membrane Protein Topology by Substituted Cysteine Accessibility Method (SCAM™). Methods Mol Biol 2017; 1615:105-128. [PMID: 28667607 DOI: 10.1007/978-1-4939-7033-9_9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A described simple and advanced protocol for the substituted-cysteine accessibility method as applied to transmembrane (TM) orientation (SCAM™) permits a topology analysis of proteins in their native state and can be universally adapted to any membrane system to either systematically map an uniform topology or identify and quantify the degree of mixed topology. In this approach, noncritical individual amino acids that are thought to reside in the putative extracellular or intracellular loops of a membrane protein are replaced one at a time by cysteine residue, and the orientation with respect to the membrane is evaluated using a pair of membrane-impermeable nondetectable and detectable thiol-reactive labeling reagents.
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Affiliation(s)
- Mikhail Bogdanov
- Department of Biochemistry & Molecular Biology, University of Texas Health Science Center at Houston, McGovern Medical School, UT-GSBS, P.O. Box 20334, Houston, TX, 77030, USA.
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