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Murphy BT, Wiepen JJ, Graham DE, Swanson SK, Kashipathy MM, Cooper A, Battaile KP, Johnson DK, Florens L, Blevins JS, Lovell S, Zückert WR. Borrelia burgdorferi BB0346 is an Essential, Structurally Variant LolA Homolog that is Primarily Required for Homeostatic Localization of Periplasmic Lipoproteins. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.06.606844. [PMID: 39149330 PMCID: PMC11326224 DOI: 10.1101/2024.08.06.606844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
In diderm bacteria, the Lol pathway canonically mediates the periplasmic transport of lipoproteins from the inner membrane (IM) to the outer membrane (OM) and therefore plays an essential role in bacterial envelope homeostasis. After extrusion of modified lipoproteins from the IM via the LolCDE complex, the periplasmic chaperone LolA carries lipoproteins through the periplasm and transfers them to the OM lipoprotein insertase LolB, itself a lipoprotein with a LolA-like fold. Yet, LolB homologs appear restricted to γ-proteobacteria and are missing from spirochetes like the tick-borne Lyme disease pathogen Borrelia burgdorferi, suggesting a different hand-off mechanism at the OM. Here, we solved the crystal structure of the B. burgdorferi LolA homolog BB0346 (LolABb) at 1.9 Å resolution. We identified multiple structural deviations in comparative analyses to other solved LolA structures, particularly a unique LolB-like protruding loop domain. LolABb failed to complement an Escherichia coli lolA knockout, even after codon optimization, signal I peptide adaptation, and a C-terminal chimerization which had allowed for complementation with an α-proteobacterial LolA. Analysis of a conditional B. burgdorferi lolA knockout strain indicated that LolABb was essential for growth. Intriguingly, protein localization assays indicated that initial depletion of LolABb led to an emerging mislocalization of both IM and periplasmic OM lipoproteins, but not surface lipoproteins. Together, these findings further support the presence of two separate primary secretion pathways for periplasmic and surface OM lipoproteins in B. burgdorferi and suggest that the distinct structural features of LolABb allow it to function in a unique LolB-deficient lipoprotein sorting system.
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Affiliation(s)
- Bryan T. Murphy
- University of Kansas School of Medicine, Department of Microbiology, Molecular Genetics & Immunology, Kansas City, Kansas
| | - Jacob J. Wiepen
- University of Kansas School of Medicine, Department of Microbiology, Molecular Genetics & Immunology, Kansas City, Kansas
| | - Danielle E. Graham
- University of Arkansas for Medical Sciences, Department of Microbiology & Immunology, Little Rock, Arkansas
| | | | - Maithri M. Kashipathy
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, Washington, 98109, USA
| | - Anne Cooper
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, Washington, 98109, USA
- University of Kansas, Protein Structure and X-ray Crystallography Laboratory, Lawrence, Kansas
| | | | - David K. Johnson
- University of Kansas, Protein Structure and X-ray Crystallography Laboratory, Lawrence, Kansas
| | | | - Jon S. Blevins
- University of Arkansas for Medical Sciences, Department of Microbiology & Immunology, Little Rock, Arkansas
| | - Scott Lovell
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, Washington, 98109, USA
- University of Kansas, Protein Structure and X-ray Crystallography Laboratory, Lawrence, Kansas
| | - Wolfram R. Zückert
- University of Kansas School of Medicine, Department of Microbiology, Molecular Genetics & Immunology, Kansas City, Kansas
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Sposato D, Mercolino J, Torrini L, Sperandeo P, Lucidi M, Alegiani R, Varone I, Molesini G, Leoni L, Rampioni G, Visca P, Imperi F. Redundant essentiality of AsmA-like proteins in Pseudomonas aeruginosa. mSphere 2024; 9:e0067723. [PMID: 38305166 PMCID: PMC10900882 DOI: 10.1128/msphere.00677-23] [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: 11/02/2023] [Accepted: 01/03/2024] [Indexed: 02/03/2024] Open
Abstract
The outer membrane (OM) is an essential structure of Gram-negative bacteria that provides mechanical strength and protection from large and/or hydrophobic toxic molecules, including many antibiotics. The OM is composed of glycerophospholipids (GPLs) and lipopolysaccharide (LPS) in the inner and outer leaflets, respectively, and hosts integral β-barrel proteins and lipoproteins. While the systems responsible for translocation and insertion of LPS and OM proteins have been elucidated, the mechanism(s) mediating transport of GPLs from the inner membrane to the OM has remained elusive for decades. Very recently, studies performed in Escherichia coli proposed a role in this process for AsmA-like proteins that are predicted to share structural features with eukaryotic lipid transporters. In this study, we provide the first systematic investigation of AsmA-like proteins in a bacterium other than E. coli, the opportunistic human pathogen Pseudomonas aeruginosa. Bioinformatic analyses revealed that P. aeruginosa possesses seven AsmA-like proteins. Deletion of asmA-like genes in many different combinations, coupled with conditional mutagenesis, revealed that four AsmA-like proteins are redundantly essential for growth and OM integrity in P. aeruginosa, including a novel AsmA-like protein (PA4735) that is not present in E. coli. Cells depleted of AsmA-like proteins showed severe defects in the OM permeability barrier that were partially rescued by lowering the synthesis or transport of LPS. Since fine balancing of GPL and LPS levels is crucial for OM integrity, this evidence supports the role of AsmA-like proteins in GPL transport toward the OM. IMPORTANCE Given the importance of the outer membrane (OM) for viability and antibiotic resistance in Gram-negative bacteria, in the last decades, several studies have focused on the characterization of the systems involved in OM biogenesis, which have also been explored as targets for antibacterial drug development. However, the mechanism mediating translocation of glycerophospholipids (GPLs) to the OM remained unknown until recent studies provided evidence that AsmA-like proteins could be responsible for this process. Here, we demonstrate for the first time that AsmA-like proteins are essential and redundant for growth and OM integrity in a Gram-negative bacterium other than the model organism Escherichia coli and demonstrate that the human pathogen Pseudomonas aeruginosa has an additional essential AsmA-like protein that is not present in E. coli, thus expanding the range of AsmA-like proteins that play key functions in Gram-negative bacteria.
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Affiliation(s)
| | | | - Luisa Torrini
- Department of Science, University Roma Tre, Rome, Italy
| | - Paola Sperandeo
- Department of Pharmacological and Biomolecular Sciences, University of Milano, Milan, Italy
| | - Massimiliano Lucidi
- Department of Science, University Roma Tre, Rome, Italy
- NBFC, National Biodiversity Future Center, Palermo, Italy
| | | | - Ilaria Varone
- Department of Science, University Roma Tre, Rome, Italy
| | | | - Livia Leoni
- Department of Science, University Roma Tre, Rome, Italy
| | - Giordano Rampioni
- Department of Science, University Roma Tre, Rome, Italy
- IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Paolo Visca
- Department of Science, University Roma Tre, Rome, Italy
- NBFC, National Biodiversity Future Center, Palermo, Italy
- IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Francesco Imperi
- Department of Science, University Roma Tre, Rome, Italy
- NBFC, National Biodiversity Future Center, Palermo, Italy
- IRCCS Fondazione Santa Lucia, Rome, Italy
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Lehman KM, May KL, Marotta J, Grabowicz M. Genetic analysis reveals a robust and hierarchical recruitment of the LolA chaperone to the LolCDE lipoprotein transporter. mBio 2024; 15:e0303923. [PMID: 38193657 PMCID: PMC10865981 DOI: 10.1128/mbio.03039-23] [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: 11/10/2023] [Accepted: 11/29/2023] [Indexed: 01/10/2024] Open
Abstract
The outer membrane (OM) is an essential organelle of Gram-negative bacteria. Lipoproteins are key to building the OM, performing essential functions in several OM assembly machines. Lipoproteins mature in the inner membrane (IM) and are then trafficked to the OM. In Escherichia coli, the LolCDE transporter is needed to extract lipoproteins from the IM to begin trafficking. Lipoproteins are then transferred from LolCDE to the periplasmic chaperone LolA which ferries them to the OM for insertion by LolB. LolA recruitment by LolC is an essential trafficking step. Structural and biochemical studies suggested that two regions (termed Hook and Pad) within a periplasmic loop of LolC worked in tandem to recruit LolA, leading to a bipartite model for recruitment. Here, we genetically examine the LolC periplasmic loop in vivo using E. coli. Our findings challenge the bipartite interaction model. We show that while the Hook is essential for lipoprotein trafficking in vivo, lipoproteins are still efficiently trafficked when the Pad residues are inactivated. We show with AlphaFold2 multimer modeling that Hook:LolA interactions are likely universal among diverse Gram-negative bacteria. Conversely, Pad:LolA interactions vary across phyla. Our in vivo data redefine LolC:LolA recruitment into a hierarchical interaction model. We propose that the Hook is the major player in LolA recruitment, while the Pad plays an ancillary role that is important for efficiency but is ultimately dispensable. Our findings expand the understanding of a fundamental step in essential lipoprotein trafficking and have implications for efforts to develop new antibacterials that target LolCDE.IMPORTANCEResistance to current antibiotics is increasingly common. New antibiotics that target essential processes are needed to expand clinical options. For Gram-negative bacteria, their cell surface-the outer membrane (OM)-is an essential organelle and antibiotic barrier that is an attractive target for new antibacterials. Lipoproteins are key to building the OM. The LolCDE transporter is needed to supply the OM with lipoproteins and has been a focus of recent antibiotic discovery. In vitro evidence recently proposed a two-part interaction of LolC with LolA lipoprotein chaperone (which traffics lipoproteins to the OM) via "Hook" and "Pad" regions. We show that this model does not reflect lipoprotein trafficking in vivo. Only the Hook is essential for lipoprotein trafficking and is remarkably robust to mutational changes. The Pad is non-essential for lipoprotein trafficking but plays an ancillary role, contributing to trafficking efficiency. These insights inform ongoing efforts to drug LolCDE.
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Affiliation(s)
- Kelly M. Lehman
- Microbiology and Molecular Genetics Program, Graduate Division of Biological and Biomedical Sciences, Laney Graduate School, Emory University, Atlanta, Georgia, USA
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Kerrie L. May
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Julianna Marotta
- Microbiology and Molecular Genetics Program, Graduate Division of Biological and Biomedical Sciences, Laney Graduate School, Emory University, Atlanta, Georgia, USA
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Marcin Grabowicz
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA
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Lehman KM, May KL, Marotta J, Grabowicz M. Genetic analysis reveals a robust and hierarchical recruitment of the LolA chaperone to the LolCDE lipoprotein transporter. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.08.566237. [PMID: 37986794 PMCID: PMC10659402 DOI: 10.1101/2023.11.08.566237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
The outer membrane (OM) is an essential organelle of Gram-negative bacteria. Lipoproteins are key to building the OM, performing essential functions in several OM assembly machines. Lipoproteins mature in the inner membrane (IM) and are then trafficked to the OM. In Escherichia coli, the LolCDE transporter is needed to extract lipoproteins from the IM to begin trafficking. Lipoproteins are then transferred from LolCDE to the periplasmic chaperone LolA which ferries them to the OM for insertion by LolB. LolA recruitment by LolC is an essential trafficking step. Structural and biochemical studies suggested that two regions (termed Hook and Pad) within a periplasmic loop of LolC worked in tandem to recruit LolA, leading to a bipartite model for recruitment. Here, we genetically examine the LolC periplasmic loop in vivo using E. coli. Our findings challenge the bipartite interaction model. We show that while the Hook is essential for lipoprotein trafficking in vivo, lipoproteins are still efficiently trafficked when the Pad residues are inactivated. We show with AlphaFold2 multimer modeling that Hook:LolA interactions are likely universal among diverse Gram-negative bacteria. Conversely, Pad:LolA interactions vary across phyla. Our in vivo data redefine LolC:LolA recruitment into a hierarchical interaction model. We propose that the Hook is the major player in LolA recruitment, while the Pad plays an ancillary role that is important for efficiency but is ultimately dispensable. Our findings expand the understanding of a fundamental step in essential lipoprotein trafficking and have implications for efforts to develop new antibacterials that target LolCDE.
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Affiliation(s)
- Kelly M. Lehman
- Microbiology and Molecular Genetics Program, Graduate Division of Biological and Biomedical Sciences, Laney Graduate School, Emory University, Atlanta, Georgia, USA
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA
- Kelly M. Lehman and Kerrie L. May contributed equally to this work. Author order was determined alphabetically
| | - Kerrie L. May
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA
- Kelly M. Lehman and Kerrie L. May contributed equally to this work. Author order was determined alphabetically
| | - Julianna Marotta
- Microbiology and Molecular Genetics Program, Graduate Division of Biological and Biomedical Sciences, Laney Graduate School, Emory University, Atlanta, Georgia, USA
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Marcin Grabowicz
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA
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Jaiman D, Nagampalli R, Persson K. A comparative analysis of lipoprotein transport proteins: LolA and LolB from Vibrio cholerae and LolA from Porphyromonas gingivalis. Sci Rep 2023; 13:6605. [PMID: 37095149 PMCID: PMC10126205 DOI: 10.1038/s41598-023-33705-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 04/18/2023] [Indexed: 04/26/2023] Open
Abstract
In Gram-negative bacteria, N-terminal lipidation is a signal for protein trafficking from the inner membrane (IM) to the outer membrane (OM). The IM complex LolCDE extracts lipoproteins from the membrane and moves them to the chaperone LolA. The LolA-lipoprotein complex crosses the periplasm after which the lipoprotein is anchored to the OM. In γ-proteobacteria anchoring is assisted by the receptor LolB, while a corresponding protein has not been identified in other phyla. In light of the low sequence similarity between Lol-systems from different phyla and that they may use different Lol components, it is crucial to compare representative proteins from several species. Here we present a structure-function study of LolA and LolB from two phyla: LolA from Porphyromonas gingivalis (phylum bacteroidota), and LolA and LolB from Vibrio cholerae (phylum proteobacteria). Despite large sequence differences, the LolA structures are very similar, hence structure and function have been conserved throughout evolution. However, an Arg-Pro motif crucial for function in γ-proteobacteria has no counterpart in bacteroidota. We also show that LolA from both phyla bind the antibiotic polymyxin B whereas LolB does not. Collectively, these studies will facilitate the development of antibiotics as they provide awareness of both differences and similarities across phyla.
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Affiliation(s)
- Deepika Jaiman
- Umeå Centre for Microbial Research (UCMR), Umeå, Sweden
- Department of Chemistry, Umeå University, 90187, Umeå, Sweden
| | - Raghavendra Nagampalli
- Umeå Centre for Microbial Research (UCMR), Umeå, Sweden
- Department of Chemistry, Umeå University, 90187, Umeå, Sweden
| | - Karina Persson
- Umeå Centre for Microbial Research (UCMR), Umeå, Sweden.
- Department of Chemistry, Umeå University, 90187, Umeå, Sweden.
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Vercruysse M, Dylus D. Special issue of BBA reviews — Molecular Cell Research: The Gram-negative envelope and potential targets for novel antibiotics. BIOCHIMICA ET BIOPHYSICA ACTA (BBA) - MOLECULAR CELL RESEARCH 2023; 1870:119472. [PMID: 37011731 DOI: 10.1016/j.bbamcr.2023.119472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 02/08/2023] [Accepted: 02/27/2023] [Indexed: 04/03/2023]
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