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Chen C, Song M, Li K, Yan S, Chen M, Geng J. E. coli outer membrane protein T (OmpT) nanopore for peptide sensing. Biochem Biophys Res Commun 2023; 677:132-140. [PMID: 37586211 DOI: 10.1016/j.bbrc.2023.05.125] [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: 04/24/2023] [Accepted: 05/31/2023] [Indexed: 08/18/2023]
Abstract
Peptide detection methods with facility and high sensitivity are essential for diagnosing disease associated with peptide biomarkers. Nanopore sensing technology had emerged as a low cost, high-throughput, and scalable tool for peptide detection. The omptins family proteins which can form β-barrel pores have great potentials to be developed as nanopore biosensor. However, there are no study about the channel properties of E. coli OmpT and the development of OmpT as a nanopore biosensor. In this study, the OmpT biological nanopore channel was constructed with a conductance of 1.49 nS in 500 mM NaCl buffer and a three-step gating phenomenon under negative voltage higher than 100 mV and then was developed as a peptide biosensor which can detect peptide without the interfere of ssDNA and dNTPs. The OmpT constructed in this study has potential application in peptide detection, and also provides a new idea for the detection of peptides using the specific binding ability of protease.
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Affiliation(s)
- Chuan Chen
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China; School of Pharmacy, North Sichuan Medical College, Nanchong, 637000, China
| | - Mengxiao Song
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China
| | - Kaiju Li
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China
| | - Shixin Yan
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China
| | - Mutian Chen
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China
| | - Jia Geng
- Department of Laboratory Medicine, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, 610041, China; Tianfu Jincheng Laboratory, City of Future Medicine, Chengdu 641400, China.
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2
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Chumjan W, Sangchalee A, Somwang C, Mookda N, Yaikeaw S, Somsakeesit LO. Outer membrane protein N expressed in Gram-negative bacterial strain of Escherichia coli BL21 (DE3) Omp8 Rosetta strains under osmoregulation by salts, sugars, and pHs. PLoS One 2023; 18:e0288096. [PMID: 37535641 PMCID: PMC10399875 DOI: 10.1371/journal.pone.0288096] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 06/19/2023] [Indexed: 08/05/2023] Open
Abstract
This study presented the expression of the outer membrane protein N in E. coli BL21 (DE3) Omp8 Rosetta under its growth condition and by osmoregulation. The effects of osmotic stress caused by salts, sugars, or pH values on the survival of the target Gram-negative bacterial strain of E. coli BL21 (DE3) Omp8 Rosetta and OmpN expression remain unknown. Here, tryptone yeast extract with varied salts and concentrations was initially used to generate an LB broth medium. To show how salts and concentration affect bacterial growth, the optical density at 600 nm was measured. The findings supported the hypothesis that salts and concentrations control bacterial growth. Moreover, a Western blotting study revealed that OmpN overexpression was present in all tested salts after stimulation with both glucose and fructose after being treated individually with anti-OmpN and anti-histidine tag polyclonal antibodies on transferred nitrocellulose membrane containing crude OmpN. Following the presence of the plasmid pET21b(+)/ompN-BOR into E. coli BL21 (DE3) Omp8 Rosetta, which was expressed in the recombinant OmpN protein (BOR), OmpN expression was demonstrated for all monovalent cations as well as MgCl2. All of the tested salts, except for BaCl2, NaH2PO4, and KH2PO4, showed overexpression of recombinant BOR after Isopropyl β-D-1-thiogalactopyranoside (IPTG) induction. Using CH3COONa, both with and without IPTG induction, there was very little bacterial growth and no OmpN expression. With NaCl, a pH value of 7 was suitable for bacterial development, whereas KCl required a pH value of 8. According to this research, bacterial growth in addition to salts, sugars, and pH values influences how the OmpN protein is produced.
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Affiliation(s)
- Watcharin Chumjan
- Department of Chemistry, Rajamangala University of Technology Isan Khon Kaen Campus, Khon Kaen, Thailand
| | - Akira Sangchalee
- Department of Chemistry, Rajamangala University of Technology Isan Khon Kaen Campus, Khon Kaen, Thailand
| | - Cholthicha Somwang
- Department of Chemistry, Rajamangala University of Technology Isan Khon Kaen Campus, Khon Kaen, Thailand
| | - Nattida Mookda
- Department of Chemistry, Rajamangala University of Technology Isan Khon Kaen Campus, Khon Kaen, Thailand
| | - Sriwannee Yaikeaw
- Department of Chemistry, Rajamangala University of Technology Isan Khon Kaen Campus, Khon Kaen, Thailand
| | - La-Or Somsakeesit
- Department of Chemistry, Rajamangala University of Technology Isan Khon Kaen Campus, Khon Kaen, Thailand
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3
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Yu T, Omarova M, Zhang M, Hossain I, Chen J, Darvish O, John VT, Zhang D. Uncovering the Optimal Molecular Characteristics of Hydrophobe-Containing Polypeptoids to Induce Liposome or Cell Membrane Fragmentation. Biomacromolecules 2023; 24:1511-1521. [PMID: 36802533 PMCID: PMC10015453 DOI: 10.1021/acs.biomac.3c00028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Cellular functions of membrane proteins are strongly coupled to their structures and aggregation states in the cellular membrane. Molecular agents that can induce the fragmentation of lipid membranes are highly sought after as they are potentially useful for extracting membrane proteins in their native lipid environment. Toward this goal, we investigated the fragmentation of synthetic liposome using hydrophobe-containing polypeptoids (HCPs), a class of facially amphiphilic pseudo-peptidic polymers. A series of HCPs with varying chain lengths and hydrophobicities have been designed and synthesized. The effects of polymer molecular characteristics on liposome fragmentation are systemically investigated by a combination of light scattering (SLS/DLS) and transmission electron microscopy (cryo-TEM and negative stained TEM) methods. We demonstrate that HCPs with a sufficient chain length (DPn ≈ 100) and intermediate hydrophobicity (PNDG mol % = 27%) can most effectively induce the fragmentation of liposomes into colloidally stable nanoscale HCP-lipid complexes owing to the high density of local hydrophobic contact between the HCP polymers and lipid membranes. The HCPs can also effectively induce the fragmentation of bacterial lipid-derived liposomes and erythrocyte ghost cells (i.e., empty erythrocytes) to form nanostructures, highlighting the potential of HCPs as novel macromolecular surfactants toward the application of membrane protein extraction.
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Affiliation(s)
- Tianyi Yu
- Department
of Chemistry and Macromolecular Studies Group, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Marzhana Omarova
- Department
of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Meng Zhang
- Department
of Chemistry and Macromolecular Studies Group, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Istiak Hossain
- Department
of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Jianqiang Chen
- Department
of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Omead Darvish
- Department
of Chemistry and Macromolecular Studies Group, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Vijay T. John
- Department
of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Donghui Zhang
- Department
of Chemistry and Macromolecular Studies Group, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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4
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de Jonge EF, Balhuizen MD, van Boxtel R, Wu J, Haagsman HP, Tommassen J. Heat shock enhances outer-membrane vesicle release in Bordetella spp. CURRENT RESEARCH IN MICROBIAL SCIENCES 2021; 2:100009. [PMID: 34841303 PMCID: PMC8610307 DOI: 10.1016/j.crmicr.2020.100009] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 09/05/2020] [Indexed: 01/06/2023] Open
Abstract
Pertussis, also known as whooping cough, is caused by the Gram-negative bacterium Bordetella pertussis, an obligate human pathogen. Despite high vaccination rates in high-income countries, resurgence of pertussis cases is an occurring problem that urges the necessity of developing an improved vaccine. Likewise, the efficacy of vaccines for Bordetella bronchiseptica, which causes similar disease in pigs and companion animals, is debatable. A promising approach for novel vaccines is the use of outer membrane vesicles (OMVs). However, spontaneous OMV (sOMV) release by Bordetella spp. is too low for cost-effective vaccine production. Therefore, we investigated the influence of growth in various media commonly used for culturing Bordetella in the Bvg+, i.e. virulent, phase and of a heat shock applied to inactivate the cells on OMV production. Inactivation of the bacterial cells at 56 °C before OMV isolation greatly enhanced OMV release in both Bordetella spp. without causing significant cell lysis. The growth medium used barely affected the efficiency of OMV release but did affect the protein pattern of the OMVs. Differences were found to be related, at least in part, to different availability of the nutrient metals iron and zinc in the media and include expression of potentially relevant vaccine antigens, such as the receptors FauA and ZnuD. The protein content of OMVs released by heat shock was comparable to that of sOMVs as determined by SDS-PAGE and Western blot analysis, and their heat-modifiable electrophoretic mobility suggests that also protein conformation is unaffected. However, significant differences were noticed between the protein content of OMVs and that of a purified outer membrane fraction, with two major outer membrane proteins, porin OmpP and the peptidoglycan-associated RmpM, being underrepresented in the OMVs. Altogether, these results indicate that the application of a heat shock is potentially an important step in the development of cost-effective, OMV-based vaccines for both Bordetella spp.
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Affiliation(s)
- Eline F. de Jonge
- Section Molecular Microbiology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
- Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Melanie D. Balhuizen
- Section Molecular Host Defence, Division Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
| | - Ria van Boxtel
- Section Molecular Microbiology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
| | - Jianjun Wu
- Section Molecular Microbiology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
| | - Henk P. Haagsman
- Section Molecular Host Defence, Division Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
| | - Jan Tommassen
- Section Molecular Microbiology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
- Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
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Mahler F, Meister A, Vargas C, Durand G, Keller S. Self-Assembly of Protein-Containing Lipid-Bilayer Nanodiscs from Small-Molecule Amphiphiles. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2103603. [PMID: 34674382 DOI: 10.1002/smll.202103603] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Revised: 08/24/2021] [Indexed: 06/13/2023]
Abstract
When membrane proteins are removed from their natural environment, the quality of the membrane-solubilizing agent used is critical for preserving their native structures and functions. Nanodiscs that retain a lipid-bilayer core around membrane proteins have attracted great attention because they offer a much more native-like environment than detergent micelles. Here, two small-molecule amphiphiles with diglucose headgroups and either a hydrocarbon or a fluorocarbon hydrophobic chain are shown to directly assemble lipids and membrane proteins to form native nanodiscs rather than mixed micelles. Self-assembly of nanodiscs of increasing complexity from both defined, artificial vesicles as well as complex, cellular membranes is demonstrated. A detailed investigation of bilayer integrity and membrane-protein activity in these nanodiscs reveals gentle effects on the encapsulated bilayer core. The fluorinated amphiphile appears particularly promising because its lipophobicity results in gentle, non-perturbing interactions with the nanoscale lipid bilayer. A sequential model of nanodisc self-assembly is proposed that proceeds through perforation of the original membrane followed by saturation and complete solubilization of the bilayer. On this basis, pseudophase diagrams are established for mixtures of lipids and nanodisc-forming diglucoside amphiphiles, and the latter are used for the extraction of a broad range of membrane proteins from cellular membranes.
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Affiliation(s)
- Florian Mahler
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), 67663, Kaiserslautern, Germany
| | - Annette Meister
- HALOmem and Institute of Biochemistry, Martin-Luther-Universität Halle-Wittenberg, 06108, Halle (Saale), Germany
| | - Carolyn Vargas
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), 67663, Kaiserslautern, Germany
- Biophysics, Institute of Molecular Biosciences (IMB), NAWI Graz, University of Graz, Graz, 8010, Austria
- Field of Excellence BioHealth, University of Graz, Graz, Austria
- BioTechMed-Graz, Graz, Austria
| | - Grégory Durand
- Equipe Chimie Bioorganique et Systèmes Amphiphiles, Institut des Biomolécules Max Mousseron, Avignon University, Avignon, 84916, France
- CHEM2STAB, Avignon, 84916, France
| | - Sandro Keller
- Molecular Biophysics, Technische Universität Kaiserslautern (TUK), 67663, Kaiserslautern, Germany
- Biophysics, Institute of Molecular Biosciences (IMB), NAWI Graz, University of Graz, Graz, 8010, Austria
- Field of Excellence BioHealth, University of Graz, Graz, Austria
- BioTechMed-Graz, Graz, Austria
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6
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Ohnishi S, Kamiya K. Formation of Giant Lipid Vesicle Containing Dual Functions Facilitates Outer Membrane Phospholipase. ACS Synth Biol 2021; 10:1837-1846. [PMID: 34258991 DOI: 10.1021/acssynbio.0c00468] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Giant lipid vesicles are used to study artificial cell models, as well as the encapsulation of biomolecules, and the reconstitution of membrane proteins on these vesicles. Recently, complex reactions in giant vesicles have been controlled by reconstituting numerous kinds of biomolecules. However, it is challenging to generate giant lipid vesicles containing a diverse set of proteins at concentrations sufficient to ensure proper functioning. Here, we describe an artificial cell model showing dual functions of small molecule transportation and small vesicle budding, using a dual functional membrane protein (transportation and phosphatase activity) called the outer membrane phospholipase (OmpLA). To the best of our knowledge, we have revealed for the first time the transportation of ions or small molecules through OmpLA on the charged lipid bilayer. The lipid composition controlled the orientation of OmpLA through proteinase K digestion. Finally, OmpLA enzyme activity of phospholipid hydrolysis caused the budding of small vesicles.
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Affiliation(s)
- Seren Ohnishi
- Division of Molecular Science, Graduate School of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan
| | - Koki Kamiya
- Division of Molecular Science, Graduate School of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan
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7
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Bakholdina SI, Stenkova AM, Bystritskaya EP, Sidorin EV, Kim NY, Menchinskaya ES, Gorpenchenko TY, Aminin DL, Shved NA, Solov’eva TF. Studies on the Structure and Properties of Membrane Phospholipase A 1 Inclusion Bodies Formed at Low Growth Temperatures Using GFP Fusion Strategy. Molecules 2021; 26:molecules26133936. [PMID: 34203222 PMCID: PMC8271855 DOI: 10.3390/molecules26133936] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Revised: 06/08/2021] [Accepted: 06/22/2021] [Indexed: 11/23/2022] Open
Abstract
The effect of cultivation temperatures (37, 26, and 18 °C) on the conformational quality of Yersinia pseudotuberculosis phospholipase A1 (PldA) in inclusion bodies (IBs) was studied using green fluorescent protein (GFP) as a folding reporter. GFP was fused to the C-terminus of PldA to form the PldA-GFP chimeric protein. It was found that the maximum level of fluorescence and expression of the chimeric protein is observed in cells grown at 18 °C, while at 37 °C no formation of fluorescently active forms of PldA-GFP occurs. The size, stability in denaturant solutions, and enzymatic and biological activity of PldA-GFP IBs expressed at 18 °C, as well as the secondary structure and arrangement of protein molecules inside the IBs, were studied. Solubilization of the chimeric protein from IBs in urea and SDS is accompanied by its denaturation. The obtained data show the structural heterogeneity of PldA-GFP IBs. It can be assumed that compactly packed, properly folded, proteolytic resistant, and structurally less organized, susceptible to proteolysis polypeptides can coexist in PldA-GFP IBs. The use of GFP as a fusion partner improves the conformational quality of PldA, but negatively affects its enzymatic activity. The PldA-GFP IBs are not toxic to eukaryotic cells and have the property to penetrate neuroblastoma cells. Data presented in the work show that the GFP-marker can be useful not only as target protein folding indicator, but also as a tool for studying the molecular organization of IBs, their morphology, and localization in E. coli, as well as for visualization of IBs interactions with eukaryotic cells.
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Affiliation(s)
- Svetlana I. Bakholdina
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far-Eastern Branch of the Russian Academy of Sciences, Prospekt 100-let Vladivostoku 159, 690022 Vladivostok, Russia; (E.P.B.); (E.V.S.); (N.Y.K.); (E.S.M.); (D.L.A.)
- Correspondence: (S.I.B.); (T.F.S.); Tel.: +7-423-231-11-58 (S.I.B. & T.F.S.); Fax: +7-423-231-40-50 (S.I.B. & T.F.S.)
| | - Anna M. Stenkova
- Department of Medical Biology and Biotechnology, FEFU Campus, School of Biomedicine, Far Eastern Federal University, Russky Island Ajax Bay 10, 690922 Vladivostok, Russia; (A.M.S.); (N.A.S.)
| | - Evgenia P. Bystritskaya
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far-Eastern Branch of the Russian Academy of Sciences, Prospekt 100-let Vladivostoku 159, 690022 Vladivostok, Russia; (E.P.B.); (E.V.S.); (N.Y.K.); (E.S.M.); (D.L.A.)
| | - Evgeniy V. Sidorin
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far-Eastern Branch of the Russian Academy of Sciences, Prospekt 100-let Vladivostoku 159, 690022 Vladivostok, Russia; (E.P.B.); (E.V.S.); (N.Y.K.); (E.S.M.); (D.L.A.)
| | - Natalya Yu. Kim
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far-Eastern Branch of the Russian Academy of Sciences, Prospekt 100-let Vladivostoku 159, 690022 Vladivostok, Russia; (E.P.B.); (E.V.S.); (N.Y.K.); (E.S.M.); (D.L.A.)
| | - Ekaterina S. Menchinskaya
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far-Eastern Branch of the Russian Academy of Sciences, Prospekt 100-let Vladivostoku 159, 690022 Vladivostok, Russia; (E.P.B.); (E.V.S.); (N.Y.K.); (E.S.M.); (D.L.A.)
| | - Tatiana Yu. Gorpenchenko
- Federal Scientific Center of the East Asia Terrestrial Biodiversity, Far Eastern Branch of the Russian Academy of Sciences, Prospect 100-let Vladivostoku, 159, 690022 Vladivostok, Russia;
| | - Dmitry L. Aminin
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far-Eastern Branch of the Russian Academy of Sciences, Prospekt 100-let Vladivostoku 159, 690022 Vladivostok, Russia; (E.P.B.); (E.V.S.); (N.Y.K.); (E.S.M.); (D.L.A.)
- Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, 100, Shih-Chuan 1st Road, Kaohsiung 80708, Taiwan
| | - Nikita A. Shved
- Department of Medical Biology and Biotechnology, FEFU Campus, School of Biomedicine, Far Eastern Federal University, Russky Island Ajax Bay 10, 690922 Vladivostok, Russia; (A.M.S.); (N.A.S.)
| | - Tamara F. Solov’eva
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far-Eastern Branch of the Russian Academy of Sciences, Prospekt 100-let Vladivostoku 159, 690022 Vladivostok, Russia; (E.P.B.); (E.V.S.); (N.Y.K.); (E.S.M.); (D.L.A.)
- Correspondence: (S.I.B.); (T.F.S.); Tel.: +7-423-231-11-58 (S.I.B. & T.F.S.); Fax: +7-423-231-40-50 (S.I.B. & T.F.S.)
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8
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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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Han Y, Wang T, Chen G, Pu Q, Liu Q, Zhang Y, Xu L, Wu M, Liang H. A Pseudomonas aeruginosa type VI secretion system regulated by CueR facilitates copper acquisition. PLoS Pathog 2019; 15:e1008198. [PMID: 31790504 PMCID: PMC6907878 DOI: 10.1371/journal.ppat.1008198] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 12/12/2019] [Accepted: 11/07/2019] [Indexed: 12/13/2022] Open
Abstract
The type VI secretion system (T6SS) is widely distributed in Gram-negative bacteria, whose function is known to translocate substrates to eukaryotic and prokaryotic target cells to cause host damage or as a weapon for interbacterial competition. Pseudomonas aeruginosa encodes three distinct T6SS clusters (H1-, H2-, and H3-T6SS). The H1-T6SS-dependent substrates have been identified and well characterized; however, only limited information is available for the H2- and H3-T6SSs since relatively fewer substrates for them have yet been established. Here, we obtained P. aeruginosa H2-T6SS-dependent secretomes and further characterized the H2-T6SS-dependent copper (Cu2+)-binding effector azurin (Azu). Our data showed that both azu and H2-T6SS were repressed by CueR and were induced by low concentrations of Cu2+. We also identified the Azu-interacting partner OprC, a Cu2+-specific TonB-dependent outer membrane transporter. Similar to H2-T6SS genes and azu, expression of oprC was directly regulated by CueR and was induced by low Cu2+. In addition, the Azu-OprC-mediated Cu2+ transport system is critical for P. aeruginosa cells in bacterial competition and virulence. Our findings provide insights for understanding the diverse functions of T6SSs and the role of metal ions for P. aeruginosa in bacteria-bacteria competition. The type VI secretion system (T6SS) is a specific macromolecular protein export apparatus, and widely distributed in Gram-negative bacteria. T6SS plays an important role in anti-bacterial competition or delivers effector proteins to both eukaryotic and prokaryotic cells. In the present study, we performed secretomes analysis and identified 21 substrates of P. aeruginosa H2-T6SS-dependent. Specifically, we report a Cu2+-scavenging pathway consisting of a copper transporter, OprC, and a type VI secretion system (H2-T6SS)-secreted Cu2+-binding protein, Azu. Both of them are under control of the transcriptional regulator CueR. Indeed, the Azu-OprC-mediated Cu2+ transport system is critical for P. aeruginosa cells in bacterial competition and virulence. These findings exemplify how P. aeruginosa deploys this metal system to adapt to the complex environment during evolution.
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Affiliation(s)
- Yuying Han
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, ShaanXi, China
| | - Tietao Wang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, ShaanXi, China
| | - Gukui Chen
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, ShaanXi, China
| | - Qinqin Pu
- Department of Basic Science, School of Medicine and Health Science, University of North Dakota, Grand Forks, North Dakota, United States of America
| | - Qiong Liu
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, GuangDong, China
| | - Yani Zhang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, ShaanXi, China
| | - Linghui Xu
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, GuangDong, China
| | - Min Wu
- Department of Basic Science, School of Medicine and Health Science, University of North Dakota, Grand Forks, North Dakota, United States of America
| | - Haihua Liang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, ShaanXi, China
- * E-mail:
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10
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Krainer G, Keller S, Schlierf M. Structural dynamics of membrane-protein folding from single-molecule FRET. Curr Opin Struct Biol 2019; 58:124-137. [DOI: 10.1016/j.sbi.2019.05.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 05/27/2019] [Indexed: 12/15/2022]
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11
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Ricci DP, Silhavy TJ. Outer Membrane Protein Insertion by the β-barrel Assembly Machine. EcoSal Plus 2019; 8:10.1128/ecosalplus.ESP-0035-2018. [PMID: 30869065 PMCID: PMC6419762 DOI: 10.1128/ecosalplus.esp-0035-2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
Abstract
Like all outer membrane (OM) constituents, integral OM β-barrel proteins in Gram-negative bacteria are synthesized in the cytoplasm and trafficked to the OM, where they are locally assembled into the growing OM by the ubiquitous β-barrel assembly machine (Bam). While the identities and structures of all essential and accessory Bam components have been determined, the basic mechanism of Bam-assisted OM protein integration remains elusive. Here we review mechanistic analyses of OM β-barrel protein folding and Bam dynamics and summarize recent insights that inform a general model for OM protein recognition and assembly by the Bam complex.
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Affiliation(s)
- Dante P Ricci
- Department of Early Research, Achaogen, Inc., South San Francisco, CA 94080
| | - Thomas J Silhavy
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
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12
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Bakholdina SI, Sidorin EV, Khomenko VA, Isaeva MP, Kim NY, Bystritskaya EP, Pimenova EA, Solov’eva TF. The Effect of Conditions of the Expression of the Recombinant Outer Membrane Phospholipase А1 from Yersinia pseudotuberculosis on the Structure and Properties of Inclusion Bodies. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2018. [DOI: 10.1134/s1068162018020061] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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13
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Ranava D, Caumont-Sarcos A, Albenne C, Ieva R. Bacterial machineries for the assembly of membrane-embedded β-barrel proteins. FEMS Microbiol Lett 2018; 365:4961134. [DOI: 10.1093/femsle/fny087] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 04/03/2018] [Indexed: 12/11/2022] Open
Affiliation(s)
- David Ranava
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31062 Toulouse, France
| | - Anne Caumont-Sarcos
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31062 Toulouse, France
| | - Cécile Albenne
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31062 Toulouse, France
| | - Raffaele Ieva
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31062 Toulouse, France
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14
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Krainer G, Gracia P, Frotscher E, Hartmann A, Gröger P, Keller S, Schlierf M. Slow Interconversion in a Heterogeneous Unfolded-State Ensemble of Outer-Membrane Phospholipase A. Biophys J 2017. [PMID: 28629619 DOI: 10.1016/j.bpj.2017.05.037] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Structural and dynamic investigations of unfolded proteins are important for understanding protein-folding mechanisms as well as the interactions of unfolded polypeptide chains with other cell components. In the case of outer-membrane proteins (OMPs), unfolded-state properties are of particular physiological relevance, because these proteins remain unfolded for extended periods of time during their biogenesis and rely on interactions with binding partners to support proper folding. Using a combination of ensemble and single-molecule spectroscopy, we have scrutinized the unfolded state of outer-membrane phospholipase A (OmpLA) to provide a detailed view of its structural dynamics on timescales from nanoseconds to milliseconds. We find that even under strongly denaturing conditions and in the absence of residual secondary structure, OmpLA populates an ensemble of slowly (>100 ms) interconverting and conformationally heterogeneous unfolded states that lack the fast chain-reconfiguration motions expected for an unstructured, fully unfolded chain. The drastically slowed sampling of potentially folding-competent states, as compared with a random-coil polypeptide, may contribute to the slow in vitro folding kinetics observed for many OMPs. In vivo, however, slow intramolecular long-range dynamics might be advantageous for entropically favored binding of unfolded OMPs to chaperones and, by facilitating conformational selection after release from chaperones, for preserving binding-competent conformations before insertion into the outer membrane.
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Affiliation(s)
- Georg Krainer
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Dresden, Germany; Molecular Biophysics, University of Kaiserslautern, Kaiserslautern, Germany
| | - Pablo Gracia
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Dresden, Germany
| | - Erik Frotscher
- Molecular Biophysics, University of Kaiserslautern, Kaiserslautern, Germany
| | - Andreas Hartmann
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Dresden, Germany
| | - Philip Gröger
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Dresden, Germany
| | - Sandro Keller
- Molecular Biophysics, University of Kaiserslautern, Kaiserslautern, Germany.
| | - Michael Schlierf
- B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Dresden, Germany.
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15
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Schwarzer TS, Hermann M, Krishnan S, Simmel FC, Castiglione K. Preparative refolding of small monomeric outer membrane proteins. Protein Expr Purif 2017; 132:171-181. [DOI: 10.1016/j.pep.2017.01.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 12/16/2016] [Accepted: 01/31/2017] [Indexed: 12/13/2022]
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16
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Oluwole AO, Danielczak B, Meister A, Babalola JO, Vargas C, Keller S. Solubilization of Membrane Proteins into Functional Lipid-Bilayer Nanodiscs Using a Diisobutylene/Maleic Acid Copolymer. Angew Chem Int Ed Engl 2017; 56:1919-1924. [PMID: 28079955 PMCID: PMC5299484 DOI: 10.1002/anie.201610778] [Citation(s) in RCA: 195] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 11/24/2016] [Indexed: 12/22/2022]
Abstract
Once removed from their natural environment, membrane proteins depend on membrane-mimetic systems to retain their native structures and functions. To this end, lipid-bilayer nanodiscs that are bounded by scaffold proteins or amphiphilic polymers such as styrene/maleic acid (SMA) copolymers have been introduced as alternatives to detergent micelles and liposomes for in vitro membrane-protein research. Herein, we show that an alternating diisobutylene/maleic acid (DIBMA) copolymer shows equal performance to SMA in solubilizing phospholipids, stabilizes an integral membrane enzyme in functional bilayer nanodiscs, and extracts proteins of various sizes directly from cellular membranes. Unlike aromatic SMA, aliphatic DIBMA has only a mild effect on lipid acyl-chain order, does not interfere with optical spectroscopy in the far-UV range, and does not precipitate in the presence of low millimolar concentrations of divalent cations.
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Affiliation(s)
- Abraham Olusegun Oluwole
- Molecular BiophysicsUniversity of KaiserslauternErwin-Schrödinger-Str. 1367663KaiserslauternGermany
- Department of ChemistryUniversity of Ibadan200284IbadanNigeria
| | - Bartholomäus Danielczak
- Molecular BiophysicsUniversity of KaiserslauternErwin-Schrödinger-Str. 1367663KaiserslauternGermany
| | - Annette Meister
- Institute of Chemistry and Institute of Biochemistry and BiotechnologyMartin Luther University Halle-WittenbergVon-Danckelmann-Platz 406120HalleGermany
| | | | - Carolyn Vargas
- Molecular BiophysicsUniversity of KaiserslauternErwin-Schrödinger-Str. 1367663KaiserslauternGermany
| | - Sandro Keller
- Molecular BiophysicsUniversity of KaiserslauternErwin-Schrödinger-Str. 1367663KaiserslauternGermany
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17
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Oluwole AO, Danielczak B, Meister A, Babalola JO, Vargas C, Keller S. Solubilisierung von Membranproteinen in funktionelle Lipiddoppelschicht-Nanodiscs mithilfe eines Diisobutylen/ Maleinsäure-Copolymers. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201610778] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Abraham Olusegun Oluwole
- Molekulare Biophysik; Technische Universität Kaiserslautern; Erwin-Schrödinger-Str. 13 67663 Kaiserslautern Deutschland
- Department of Chemistry; University of Ibadan; 200284 Ibadan Nigeria
| | - Bartholomäus Danielczak
- Molekulare Biophysik; Technische Universität Kaiserslautern; Erwin-Schrödinger-Str. 13 67663 Kaiserslautern Deutschland
| | - Annette Meister
- Institut für Chemie und Institut für Biochemie und Biotechnologie; Martin-Luther-Universität Halle-Wittenberg; Von-Danckelmann-Platz 4 06120 Halle Deutschland
| | | | - Carolyn Vargas
- Molekulare Biophysik; Technische Universität Kaiserslautern; Erwin-Schrödinger-Str. 13 67663 Kaiserslautern Deutschland
| | - Sandro Keller
- Molekulare Biophysik; Technische Universität Kaiserslautern; Erwin-Schrödinger-Str. 13 67663 Kaiserslautern Deutschland
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18
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Danoff EJ, Fleming KG. Novel Kinetic Intermediates Populated along the Folding Pathway of the Transmembrane β-Barrel OmpA. Biochemistry 2016; 56:47-60. [PMID: 28001375 DOI: 10.1021/acs.biochem.6b00809] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We examined the folding of the β-barrel membrane protein OmpA from Escherichia coli. Although previous studies identified several intermediate states followed by a concerted translocation mechanism across the bilayer, some aspects of the pathway were still unclear, including the extent of secondary structure formation in the intermediate states and how the mechanism gave rise to multiple exponential phases in the folding kinetics. We addressed these questions by investigating the folding kinetics of the OmpA transmembrane β-barrel domain over a range of bilayer thicknesses, allowing us to observe different regions of the folding pathway. The fastest folding into the thinnest bilayers provided information about the later stages of the process, and the slowest folding into thicker bilayers revealed early kinetic steps. Folding was monitored using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and circular dichroism spectroscopy, which provide complementary information about tertiary and secondary structure formation. We globally fit the folding data to kinetic schemes and found that the same core pathway was followed under all lipid conditions. We propose a multistep folding mechanism for OmpA that includes unstructured surface-adsorbed states converting through a partially inserted state with substantial β-sheet structure to the final natively inserted barrel. Kinetic models show that all steps of the main folding pathway are accelerated by membrane defects that occur as a result of thinning the bilayer or incubation of lipids at the phase transition temperature. In addition to suppressing off-pathway states, β-barrel assembly machinery-catalyzed folding in vivo could accelerate any or all of these main folding steps to ensure efficient outer membrane protein biogenesis in vivo.
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Affiliation(s)
- Emily J Danoff
- T. C. Jenkins Department of Biophysics, Johns Hopkins University , Baltimore, Maryland 21218, United States
| | - Karen G Fleming
- T. C. Jenkins Department of Biophysics, Johns Hopkins University , Baltimore, Maryland 21218, United States
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19
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Bakholdina SI, Tischenko NM, Sidorin EV, Isaeva MP, Likhatskaya GN, Dmitrenok PS, Kim NY, Chernikov OV, Solov'eva TF. Recombinant Phospholipase A1 of the Outer Membrane of Psychrotrophic Yersinia pseudotuberculosis: Expression, Purification, and Characterization. BIOCHEMISTRY (MOSCOW) 2016; 81:47-57. [PMID: 26885582 DOI: 10.1134/s0006297916010053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The pldA gene encoding membrane-bound phospholipase A1 of Yersinia pseudotuberculosis was cloned and expressed in Escherichia coli cells. Recombinant phospholipase A1 (rPldA) was isolated from inclusion bodies dissolved in 8 M urea by two-stage chromatography (ion-exchange and gel-filtration chromatography) as an inactive monomer. The molecular mass of the rPldA determined by MALDI-TOF MS was 31.7 ± 0.4 kDa. The highly purified rPldA was refolded by 10-fold dilution with buffer containing 10 mM Triton X-100 and subsequent incubation at room temperature for 16 h. The refolded rPldA hydrolyzed 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine in the presence of calcium ions. The enzyme exhibited maximal activity at 37°C and nearly 40% of maximal activity at 15°C. The phospholipase A1 was active over a wide range of pH from 4 to 11, exhibiting maximal activity at pH 10. Spatial structure models of the monomer and the dimer of Y. pseudotuberculosis phospholipase A1 were constructed, and functionally important amino acid residues of the enzyme were determined. Structural differences between phospholipases A1 from Y. pseudotuberculosis and E. coli, which can affect the functional activity of the enzyme, were revealed.
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Affiliation(s)
- S I Bakholdina
- Elyakov Pacific Institute of Bioorganic Chemistry, Russian Academy of Sciences, Far East Branch, Vladivostok, 690022, Russia.
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20
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Horne JE, Radford SE. A growing toolbox of techniques for studying β-barrel outer membrane protein folding and biogenesis. Biochem Soc Trans 2016; 44:802-9. [PMID: 27284045 PMCID: PMC4900752 DOI: 10.1042/bst20160020] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Indexed: 01/21/2023]
Abstract
Great strides into understanding protein folding have been made since the seminal work of Anfinsen over 40 years ago, but progress in the study of membrane protein folding has lagged behind that of their water soluble counterparts. Researchers in these fields continue to turn to more advanced techniques such as NMR, mass spectrometry, molecular dynamics (MD) and single molecule methods to interrogate how proteins fold. Our understanding of β-barrel outer membrane protein (OMP) folding has benefited from these advances in the last decade. This class of proteins must traverse the periplasm and then insert into an asymmetric lipid membrane in the absence of a chemical energy source. In this review we discuss old, new and emerging techniques used to examine the process of OMP folding and biogenesis in vitro and describe some of the insights and new questions these techniques have revealed.
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Affiliation(s)
- Jim E Horne
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, The University of Leeds, Leeds LS2 9JT, U.K
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, The University of Leeds, Leeds LS2 9JT, U.K.
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21
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Modulating bilayer mechanical properties to promote the coupled folding and insertion of an integral membrane protein. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2015; 44:503-12. [DOI: 10.1007/s00249-015-1032-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 04/23/2015] [Accepted: 05/05/2015] [Indexed: 12/17/2022]
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22
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Baker LA, Folkers GE, Sinnige T, Houben K, Kaplan M, van der Cruijsen EAW, Baldus M. Magic-angle-spinning solid-state NMR of membrane proteins. Methods Enzymol 2015; 557:307-28. [PMID: 25950971 DOI: 10.1016/bs.mie.2014.12.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Solid-state NMR spectroscopy (ssNMR) provides increasing possibilities to examine membrane proteins in different molecular settings, ranging from synthetic bilayers to whole cells. This flexibility often enables ssNMR experiments to be directly correlated with membrane protein function. In this contribution, we discuss experimental aspects of such studies starting with protein expression and labeling, leading to membrane protein isolation or to membrane proteins in a cellular environment. We show that optimized procedures can depend on aspects such as the achieved levels of expression, the stability of the protein during purification or proper refolding. Dealing with native membrane samples, such as isolated cellular membranes, can alleviate or entirely remove such biochemical challenges. Subsequently, we outline ssNMR experiments that involve the use of magic-angle-spinning and can be used to study membrane protein structure and their functional aspects. We pay specific attention to spectroscopic issues such as sensitivity and spectral resolution. The latter aspect can be controlled using a combination of tailored preparation procedures with solid-state NMR experiments that simplify the spectral analysis using specific filtering and correlation methods. Such approaches have already provided access to obtain structural views of membrane proteins and study their function in lipid bilayers. Ongoing developments in sample preparation and NMR methodology, in particular in using hyperpolarization or proton-detection schemes, offer additional opportunities to study membrane proteins close to their cellular function. These considerations suggest a further increase in the potential of using solid-state NMR in the context of prokaryotic or eukaryotic membrane protein systems in the near future.
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Affiliation(s)
- Lindsay A Baker
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Gert E Folkers
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Tessa Sinnige
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Klaartje Houben
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Mohammed Kaplan
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Elwin A W van der Cruijsen
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Marc Baldus
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
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23
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Sinnige T, Houben K, Pritisanac I, Renault M, Boelens R, Baldus M. Insight into the conformational stability of membrane-embedded BamA using a combined solution and solid-state NMR approach. JOURNAL OF BIOMOLECULAR NMR 2015; 61:321-332. [PMID: 25567766 DOI: 10.1007/s10858-014-9891-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 12/17/2014] [Indexed: 06/04/2023]
Abstract
The β-barrel assembly machinery (BAM) is involved in folding and insertion of outer membrane proteins in Gram-negative bacteria, a process that is still poorly understood. With its 790 residues, BamA presents a challenge to current NMR methods. We utilized a "divide and conquer" approach in which we first obtained resonance assignments for BamA's periplasmic POTRA domains 4 and 5 by solution NMR. Comparison of these assignments to solid-state NMR (ssNMR) data obtained on two BamA constructs including the transmembrane domain and one or two soluble POTRA domains suggested that the fold of POTRA domain 5 critically depends on the interface with POTRA 4. Using specific labeling schemes we furthermore obtained ssNMR resonance assignments for residues in the extracellular loop 6 that is known to be crucial for BamA-mediated substrate folding and insertion. Taken together, our data provide novel insights into the conformational stability of membrane-embedded, non-crystalline BamA.
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Affiliation(s)
- Tessa Sinnige
- NMR Spectroscopy, Department of Chemistry, Faculty of Science, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
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24
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Folding membrane proteins in vitro: A table and some comments. Arch Biochem Biophys 2014; 564:314-26. [DOI: 10.1016/j.abb.2014.06.029] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 06/17/2014] [Accepted: 06/23/2014] [Indexed: 12/23/2022]
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25
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Agarwal R, Zakharov S, Hasan SS, Ryan CM, Whitelegge JP, Cramer WA. Structure-function of cyanobacterial outer-membrane protein, Slr1270: homolog of Escherichia coli drug export/colicin import protein, TolC. FEBS Lett 2014; 588:3793-801. [PMID: 25218435 PMCID: PMC4288923 DOI: 10.1016/j.febslet.2014.08.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 08/18/2014] [Accepted: 08/19/2014] [Indexed: 01/07/2023]
Abstract
Compared to thylakoid and inner membrane proteins in cyanobacteria, no structure-function information is available presently for integral outer-membrane proteins (OMPs). The Slr1270 protein from the cyanobacterium Synechocystis 6803, over-expressed in Escherichia coli, was refolded, and characterized for molecular size, secondary structure, and ion-channel function. Refolded Slr1270 displays a single band in native-electrophoresis, has an α-helical content of 50-60%, as in E. coli TolC with which it has significant secondary-structure similarity, and an ion-channel function with a single-channel conductance of 80-200pS, and a monovalent ion (K(+):Cl(-)) selectivity of 4.7:1. The pH-dependence of channel conductance implies a role for carboxylate residues in channel gating, analogous to that in TolC.
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Affiliation(s)
- Rachna Agarwal
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States; Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India
| | - Stanislav Zakharov
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States; Institute of Basic Problems of Biology, Russian Academy of Sciences, Puschino, Moscow Region, Russian Federation
| | - S Saif Hasan
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States
| | - Christopher M Ryan
- Pasarow Mass Spectrometry Laboratory, NPI-Semel Institute for Neuroscience and Human Behavior, UCLA, Los Angeles, CA, United States
| | - Julian P Whitelegge
- Pasarow Mass Spectrometry Laboratory, NPI-Semel Institute for Neuroscience and Human Behavior, UCLA, Los Angeles, CA, United States
| | - William A Cramer
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States.
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26
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27
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Sinnige T, Weingarth M, Renault M, Baker L, Tommassen J, Baldus M. Solid-state NMR studies of full-length BamA in lipid bilayers suggest limited overall POTRA mobility. J Mol Biol 2014; 426:2009-21. [PMID: 24530687 DOI: 10.1016/j.jmb.2014.02.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 01/22/2014] [Accepted: 02/05/2014] [Indexed: 11/24/2022]
Abstract
The outer membrane protein BamA is the key player in β-barrel assembly in Gram-negative bacteria. Despite the availability of high-resolution crystal structures, the dynamic behavior of the transmembrane domain and the large periplasmic extension consisting of five POTRA (POlypeptide-TRansport-Associated) domains remains unclear. We demonstrate reconstitution of full-length BamA in proteoliposomes at low lipid-to-protein ratio, leading to high sensitivity and resolution in solid-state NMR (ssNMR) experiments. We detect POTRA domains in ssNMR experiments probing rigid protein segments in our preparations. These results suggest that the periplasmic region of BamA is firmly attached to the β-barrel and does not experience fast global motion around the angle between POTRA 2 and 3. We show that this behavior holds at lower protein concentrations and elevated temperatures. Chemical shift variations observed after reconstitution in lipids with different chain lengths and saturation levels are compatible with conformational plasticity of BamA's transmembrane domain. Electron microscopy of the ssNMR samples shows that BamA can cause local disruptions of the lipid bilayer in proteoliposomes. The observed interplay between protein-protein and protein-lipid interactions may be critical for BamA-mediated insertion of substrates into the outer membrane.
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Affiliation(s)
- Tessa Sinnige
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Markus Weingarth
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Marie Renault
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Lindsay Baker
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Jan Tommassen
- Department of Molecular Microbiology, Institute of Biomembranes, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Marc Baldus
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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28
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Simon S, Demeure C, Lamourette P, Filali S, Plaisance M, Créminon C, Volland H, Carniel E. Fast and simple detection of Yersinia pestis applicable to field investigation of plague foci. PLoS One 2013; 8:e54947. [PMID: 23383008 PMCID: PMC3558477 DOI: 10.1371/journal.pone.0054947] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 12/19/2012] [Indexed: 01/14/2023] Open
Abstract
Yersinia pestis, the plague bacillus, has a rodent-flea-rodent life cycle but can also persist in the environment for various periods of time. There is now a convenient and effective test (F1-dipstick) for the rapid identification of Y. pestis from human patient or rodent samples, but this test cannot be applied to environmental or flea materials because the F1 capsule is mostly produced at 37°C. The plasminogen activator (PLA), a key virulence factor encoded by a Y. pestis-specific plasmid, is synthesized both at 20°C and 37°C, making it a good candidate antigen for environmental detection of Y. pestis by immunological methods. A recombinant PLA protein from Y. pestis synthesized by an Escherichia coli strain was used to produce monoclonal antibodies (mAbs). PLA-specific mAbs devoid of cross-reactions with other homologous proteins were further cloned. A pair of mAbs was selected based on its specificity, sensitivity, comprehensiveness, and ability to react with Y. pestis strains grown at different temperatures. These antibodies were used to develop a highly sensitive one-step PLA-enzyme immunoassay (PLA-EIA) and an immunostrip (PLA-dipstick), usable as a rapid test under field conditions. These two PLA-immunometric tests could be valuable, in addition to the F1-disptick, to confirm human plague diagnosis in non-endemic areas (WHO standard case definition). They have the supplementary advantage of allowing a rapid and easy detection of Y. pestis in environmental and flea samples, and would therefore be of great value for surveillance and epidemiological investigations of plague foci. Finally, they will be able to detect natural or genetically engineered F1-negative Y. pestis strains in human patients and environmental samples.
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Affiliation(s)
- Stéphanie Simon
- CEA Saclay, iBiTec-S, Service de Pharmacologie et d'Immunoanalyse, Laboratoire d'Etudes et de Recherches en Immunoanalyse, Gif sur Yvette, France.
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29
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Wu C, Tran JC, Zamdborg L, Durbin KR, Li M, Ahlf DR, Early BP, Thomas PM, Sweedler JV, Kelleher NL. A protease for 'middle-down' proteomics. Nat Methods 2012; 9:822-4. [PMID: 22706673 PMCID: PMC3430368 DOI: 10.1038/nmeth.2074] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 05/10/2012] [Indexed: 11/15/2022]
Abstract
We developed a method for restricted enzymatic proteolysis using the outer membrane protease T (OmpT) to produce large peptides (> 6.3 kDa on average) for mass spectrometry-based proteomics. Using this approach to analyze prefractionated high-mass HeLa proteins we identified 3,697 unique peptides from 1,038 proteins. We demonstrated the ability of large OmpT peptides to differentiate closely related protein isoforms and to enable the detection of many post-translational modifications.
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Affiliation(s)
- Cong Wu
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
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30
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Hickey AJ, Hazlett KRO, Kirimanjeswara GS, Metzger DW. Identification of Francisella tularensis outer membrane protein A (FopA) as a protective antigen for tularemia. Vaccine 2011; 29:6941-7. [PMID: 21803089 DOI: 10.1016/j.vaccine.2011.07.075] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 07/08/2011] [Accepted: 07/11/2011] [Indexed: 12/31/2022]
Abstract
Francisella tularensis is a highly pathogenic gram negative bacterium that infects multiple sites in a host, including the skin and the respiratory tract, which can lead to the onset of a deadly disease with a 50% mortality rate. The live vaccine strain (LVS) of F. tularensis, while attenuated in humans but still virulent in mice, is not an option for vaccine use in the United States due to safety concerns, and currently no FDA approved vaccine exists. The purpose of the present work was to assess the ability of recombinant Francisella outer membrane protein A (FopA) to induce a protective response in mice. The gene encoding FopA from F. tularensis LVS was cloned and expressed in Escherichia coli. The resulting recombinant protein was affinity-purified from the E. coli outer membrane, incorporated into liposomes and administered to mice via multiple routes. FopA-immunized mice produced FopA-specific antibodies and were protected against both lethal intradermal and intranasal challenges with F. tularensis LVS. The vaccinated mice had reduced bacterial numbers in their lungs, livers and spleens during infection, and complete bacterial clearance was observed by day 28 post infection. Passive transfer of FopA-immune serum protected naïve mice against lethal F. tularensis LVS challenge, showing that humoral immunity played an important role in vaccine efficacy. FopA-immunization was unable to protect against challenge with the fully virulent SchuS4 strain of F. tularensis; however, the findings demonstrate proof of principle that an immune response generated against a component of a subunit vaccine is protective against lethal respiratory and intradermal tularemia.
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Affiliation(s)
- Anthony J Hickey
- Albany Medical College, Center for Immunology and Microbial Disease, Albany, NY 12208, USA
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31
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Bos MP, Tommassen J. The LptD chaperone LptE is not directly involved in lipopolysaccharide transport in Neisseria meningitidis. J Biol Chem 2011; 286:28688-28696. [PMID: 21705335 DOI: 10.1074/jbc.m111.239673] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The biosynthesis of lipopolysaccharide (LPS) in gram-negative bacteria is well understood, in contrast to the transport to its destination, the outer leaflet of the outer membrane. In Escherichia coli, synthesis and transport of LPS are essential processes. Neisseria meningitidis, conversely, can survive without LPS and tolerates inactivation of genes involved in LPS synthesis and transport. Here, we analyzed whether the LptA, LptB, LptC, LptE, LptF, and LptG proteins, recently implicated in LPS transport in E. coli, function similarly in N. meningitidis. None of the analyzed proteins was essential in N. meningitidis, consistent with their expected roles in LPS transport and additionally demonstrating that they are not required for an essential process such as phospholipid transport. As expected, the absence of most of the Lpt proteins resulted in a severe defect in LPS transport. However, the absence of LptE did not disturb transport of LPS to the cell surface. LptE was found to be associated with LptD, and its absence affected total levels of LptD, suggesting a chaperone-like role for LptE in LptD biogenesis. The absence of a direct role of LptE in LPS transport was substantiated by bioinformatic analyses showing a low conservation of LptE in LPS-producing bacteria. Apparently, the role of LptE in N. meningitidis deviates from that in E. coli, suggesting that the Lpt system does not function in a completely conserved manner in all gram-negative bacteria.
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Affiliation(s)
- Martine P Bos
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands.
| | - Jan Tommassen
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands
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33
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Tommassen J. Assembly of outer-membrane proteins in bacteria and mitochondria. Microbiology (Reading) 2010; 156:2587-2596. [DOI: 10.1099/mic.0.042689-0] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cell envelope of Gram-negative bacteria consists of two membranes separated by the periplasm. In contrast with most integral membrane proteins, which span the membrane in the form of hydrophobicα-helices, integral outer-membrane proteins (OMPs) formβ-barrels. Similarβ-barrel proteins are found in the outer membranes of mitochondria and chloroplasts, probably reflecting the endosymbiont origin of these eukaryotic cell organelles. How theseβ-barrel proteins are assembled into the outer membrane has remained enigmatic for a long time. In recent years, much progress has been reached in this field by the identification of the components of the OMP assembly machinery. The central component of this machinery, called Omp85 or BamA, is an essential and highly conserved bacterial protein that recognizes a signature sequence at the C terminus of its substrate OMPs. A homologue of this protein is also found in mitochondria, where it is required for the assembly ofβ-barrel proteins into the outer membrane as well. Although accessory components of the machineries are different between bacteria and mitochondria, a mitochondrialβ-barrel OMP can be assembled into the bacterial outer membrane and, vice versa, bacterial OMPs expressed in yeast are assembled into the mitochondrial outer membrane. These observations indicate that the basic mechanism of OMP assembly is evolutionarily highly conserved.
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Affiliation(s)
- Jan Tommassen
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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34
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Stork M, Bos MP, Jongerius I, de Kok N, Schilders I, Weynants VE, Poolman JT, Tommassen J. An outer membrane receptor of Neisseria meningitidis involved in zinc acquisition with vaccine potential. PLoS Pathog 2010; 6:e1000969. [PMID: 20617164 PMCID: PMC2895646 DOI: 10.1371/journal.ppat.1000969] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Accepted: 05/27/2010] [Indexed: 12/03/2022] Open
Abstract
Since the concentration of free iron in the human host is low, efficient iron-acquisition mechanisms constitute important virulence factors for pathogenic bacteria. In Gram-negative bacteria, TonB-dependent outer membrane receptors are implicated in iron acquisition. It is far less clear how other metals that are also scarce in the human host are transported across the bacterial outer membrane. With the aim of identifying novel vaccine candidates, we characterized in this study a hitherto unknown receptor in Neisseria meningitidis. We demonstrate that this receptor, designated ZnuD, is produced under zinc limitation and that it is involved in the uptake of zinc. Upon immunization of mice, it was capable of inducing bactericidal antibodies and we could detect ZnuD-specific antibodies in human convalescent patient sera. ZnuD is highly conserved among N. meningitidis isolates and homologues of the protein are found in many other Gram-negative pathogens, particularly in those residing in the respiratory tract. We conclude that ZnuD constitutes a promising candidate for the development of a vaccine against meningococcal disease for which no effective universal vaccine is available. Furthermore, the results suggest that receptor-mediated zinc uptake represents a novel virulence mechanism that is particularly important for bacterial survival in the respiratory tract. The outer membrane protects Gram-negative bacteria against harmful compounds from the environment. Nutrients usually pass this barrier by passive diffusion via pore-forming proteins. However, nutrients that are scarce in the environment are taken up via an active, receptor-mediated process. The vast majority of Gram-negative bacterial receptors described to date are involved in iron acquisition. Since free iron is scarce in the human host, these receptors constitute important virulence factors. In a search for putative vaccine components, we have characterized here a new receptor of Neisseria meningitidis, a resident of the nasopharynx that occasionally causes sepsis and meningitis. We show that expression of this receptor is induced under zinc limitation and that the protein is involved in the uptake of zinc. Homologues of this protein are present in many other Gram-negative pathogens, particularly in those residing in the respiratory tract, suggesting that receptor-mediated zinc acquisition is important for bacteria residing in this niche. We also found that the protein is highly conserved among N. meningitidis isolates and that it induces bactericidal antibodies upon immunization of mice. Therefore, the protein appears an excellent candidate for the development of a vaccine against N. meningitidis, for which no universal vaccine is available yet.
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Affiliation(s)
- Michiel Stork
- Department of Molecular Microbiology, Utrecht University, Utrecht, The Netherlands
| | - Martine P. Bos
- Department of Molecular Microbiology, Utrecht University, Utrecht, The Netherlands
| | - Ilse Jongerius
- Department of Molecular Microbiology, Utrecht University, Utrecht, The Netherlands
| | - Natasja de Kok
- Department of Molecular Microbiology, Utrecht University, Utrecht, The Netherlands
| | - Ingrid Schilders
- Department of Molecular Microbiology, Utrecht University, Utrecht, The Netherlands
| | | | | | - Jan Tommassen
- Department of Molecular Microbiology, Utrecht University, Utrecht, The Netherlands
- * E-mail:
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35
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Salacha R, Kovacić F, Brochier-Armanet C, Wilhelm S, Tommassen J, Filloux A, Voulhoux R, Bleves S. The Pseudomonas aeruginosa patatin-like protein PlpD is the archetype of a novel Type V secretion system. Environ Microbiol 2010; 12:1498-512. [PMID: 20192961 DOI: 10.1111/j.1462-2920.2010.02174.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We discovered a novel secreted protein by Pseudomonas aeruginosa, PlpD, as a member of the bacterial lipolytic enzyme family of patatin-like proteins (PLPs). PlpD is synthesized as a single molecule consisting of a secreted domain fused to a transporter domain. The N-terminus of PlpD includes a classical signal peptide followed by the four PLP conserved blocks that account for its lipase activity. The C-terminus consists of a POTRA (polypeptide transport-associated) motif preceding a putative 16-stranded beta-barrel similar to those of TpsB transporters of Type Vb secretion system. We showed that the C-terminus remains inserted into the outer membrane while the patatin moiety is secreted. The association between a TpsB component and a passenger protein is a unique hybrid organization that we propose to classify as Type Vd. More than 200 PlpD orthologues exist among pathogenic and environmental bacteria, which suggests that bacteria secrete numerous PLPs using this newly defined mechanism.
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Affiliation(s)
- Richard Salacha
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS-Aix Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
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36
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Zhang J, Wang SC, Lee CT. Photoreversible Conformational Changes in Membrane Proteins Using Light-Responsive Surfactants. J Phys Chem B 2009; 113:8569-80. [DOI: 10.1021/jp807875u] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jing Zhang
- Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-1211
| | - Shao-Chun Wang
- Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-1211
| | - C. Ted Lee
- Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-1211
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37
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Wang J, Cao Y, Zheng G. Mutation in the RGD motif decreases the esterase activity of Xcc_est. Biotechnol Lett 2009; 31:1445-9. [PMID: 19458922 DOI: 10.1007/s10529-009-0013-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Revised: 04/14/2009] [Accepted: 04/28/2009] [Indexed: 12/12/2022]
Abstract
Five truncated constructs of Xcc_est GDSL esterase from Xanthomonas campestris were heterologously expressed and purified. The truncated constructs with a RGD motif had higher specific activities than those without the motif. The specific activity of wild-type Xcc_est was 32.5 +/- 2.7 U/mg, while the RGD mutant was 12.5 +/- 4.9 U/mg. Moreover, we expressed mature forms of the Xcc_est protein and the RGD mutant as inclusion bodies and, after refolding, there was no significant difference between the two constructs in specific activity. These results suggest that the RGD motif affects the esterase-domain folding in vivo during the translocation process.
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Affiliation(s)
- Jianjun Wang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, 100101 Beijing, People's Republic of China
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38
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Active-site architecture and catalytic mechanism of the lipid A deacylase LpxR of Salmonella typhimurium. Proc Natl Acad Sci U S A 2009; 106:1960-4. [PMID: 19174515 DOI: 10.1073/pnas.0813064106] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The lipid A portion of lipopolysaccharide, the major component of the outer leaflet of the outer membrane of gram-negative bacteria, is toxic to humans. Modification of lipid A by enzymes often reduces its toxicity. The outer-membrane protein LpxR from Salmonella typhimurium is a lipid A-modifying enzyme. It removes the 3'-acyloxyacyl moiety of the lipid A portion of lipopolysaccharide in a Ca(2+)-dependent manner. Here, we present the crystal structure of S. typhimurium LpxR, crystallized in the presence of zinc ions. The structure, a 12-stranded beta-barrel, reveals that the active site is located between the barrel wall and an alpha-helix formed by an extracellular loop. Based on site-directed mutagenesis and modeling of a substrate on the active site, we propose a catalytic mechanism similar to that of phospholipase A2, in which a Ca(2+) forms the oxyanion hole and a histidine activates a water molecule (or a cascade of two water molecules) that subsequently attacks the carbonyl oxygen of the scissile bond.
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39
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Burgess NK, Dao TP, Stanley AM, Fleming KG. Beta-barrel proteins that reside in the Escherichia coli outer membrane in vivo demonstrate varied folding behavior in vitro. J Biol Chem 2008; 283:26748-58. [PMID: 18641391 PMCID: PMC3258919 DOI: 10.1074/jbc.m802754200] [Citation(s) in RCA: 189] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 07/18/2008] [Indexed: 11/06/2022] Open
Abstract
Little is known about the dynamic process of membrane protein folding, and few models exist to explore it. In this study we doubled the number of Escherichia coli outer membrane proteins (OMPs) for which folding into lipid bilayers has been systematically investigated. We cloned, expressed, and folded nine OMPs: outer membrane protein X (OmpX), OmpW, OmpA, the crcA gene product (PagP), OmpT, outer membrane phospholipase A (OmpLa), the fadl gene product (FadL), the yaet gene product (Omp85), and OmpF. These proteins fold into the same bilayer in vivo and share a transmembrane beta-barrel motif but vary in sequence and barrel size. We quantified the ability of these OMPs to fold into a matrix of bilayer environments. Several trends emerged from these experiments: higher pH values, thinner bilayers, and increased bilayer curvature promote folding of all OMPs. Increasing the incubation temperature promoted folding of several OMPs but inhibited folding of others. We discovered that OMPs do not have the same ability to fold into any single bilayer environment. This suggests that although environmental factors influence folding, OMPs also have intrinsic qualities that profoundly modulate their folding. To rationalize the differences in folding efficiency, we performed kinetic and thermal denaturation experiments, the results of which demonstrated that OMPs employ different strategies to achieve the observed folding efficiency.
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Affiliation(s)
| | | | | | - Karen G. Fleming
- T. C. Jenkins Department of Biophysics, Johns Hopkins University,
Baltimore, Maryland 21218
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40
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Gordon E, Horsefield R, Swarts HGP, de Pont JJHHM, Neutze R, Snijder A. Effective high-throughput overproduction of membrane proteins in Escherichia coli. Protein Expr Purif 2008; 62:1-8. [PMID: 18692139 DOI: 10.1016/j.pep.2008.07.005] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2008] [Revised: 07/01/2008] [Accepted: 07/11/2008] [Indexed: 11/16/2022]
Abstract
Structural biology is increasingly reliant on elevated throughput methods for protein production. In particular, development of efficient methods of heterologous production of membrane proteins is essential. Here, we describe the heterologous overproduction of 24 membrane proteins from the human pathogen Legionella pneumophila in Escherichia coli. Protein production was performed in 0.5 ml cultures in standard 24-well plates, allowing increased throughput with minimal effort. The effect of the location of a histidine purification tag was analyzed, and the effect of decreasing the length of the N- and C-terminal extensions introduced by the Gateway cloning strategy is presented. We observed that the location and length of the purification tag significantly affected protein production levels. In addition, an auto-induction protocol for membrane protein expression was designed to enhance the overproduction efficiency such that, regardless of the construct used, much higher expression was achieved when compared with standard induction approaches such as isopropyl-beta-d-thiogalactopyranoside (IPTG). All 24 targets were produced at levels exceeding 2mg/l, with 18 targets producing at levels of 5mg/l or higher. In summary, we have designed a fast and efficient process for the production of medically relevant membrane proteins with a minimum number of screening parameters.
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Affiliation(s)
- Euan Gordon
- Department of Chemical and Biological Engineering, Chalmers University of Technology, Box 462, 40530 Gothenburg, Sweden
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41
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Stanley AM, Fleming KG. The process of folding proteins into membranes: Challenges and progress. Arch Biochem Biophys 2008; 469:46-66. [DOI: 10.1016/j.abb.2007.09.024] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 09/17/2007] [Accepted: 09/26/2007] [Indexed: 11/28/2022]
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42
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Burgess NK, Stanley AM, Fleming KG. Determination of membrane protein molecular weights and association equilibrium constants using sedimentation equilibrium and sedimentation velocity. Methods Cell Biol 2008; 84:181-211. [PMID: 17964932 DOI: 10.1016/s0091-679x(07)84007-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Regulated molecular interactions are essential for cellular function and viability, and both homo- and hetero-interactions between all types of biomolecules play important cellular roles. This chapter focuses on interactions between membrane proteins. Knowing both the stoichiometries and stabilities of these interactions in hydrophobic environments is a prerequisite for understanding how this class of proteins regulates cellular activities in membranes. Using examples from the authors' work, this chapter highlights the application of analytical ultracentrifugation methods in the determination of these parameters for integral membrane proteins. Both theoretical and practical aspects of carrying out these experiments are discussed.
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Affiliation(s)
- Nancy K Burgess
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, USA
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43
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Huysmans GH, Radford SE, Brockwell DJ, Baldwin SA. The N-terminal helix is a post-assembly clamp in the bacterial outer membrane protein PagP. J Mol Biol 2007; 373:529-40. [PMID: 17868697 PMCID: PMC2887491 DOI: 10.1016/j.jmb.2007.07.072] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Revised: 07/23/2007] [Accepted: 07/29/2007] [Indexed: 12/04/2022]
Abstract
The Escherichia coli outer membrane beta-barrel enzyme PagP and its homologues are unique in that the eight-stranded barrel is tilted by about 25 degrees with respect to the membrane normal and is preceded by a 19-residue amphipathic alpha-helix. To investigate the role of this helix in the folding and stability of PagP, mutants were generated in which the helix was deleted (Delta(1-19)), or in which residues predicted to be involved in helix-barrel interactions were altered (W17A or R59L). The ability of the variants to insert into detergent micelles or liposomes was studied in vitro using circular dichroism, fluorescence, Fourier transform infrared spectroscopy, electrophoretic mobility and gain of enzyme activity. The data show that PagP, initially unfolded in 5% (w/v) perfluoro-octanoic acid or 6 M guanidinium chloride, inserts spontaneously and folds quantitatively to an active conformation into detergent micelles of cyclofos-7 or into large vesicles of diC(12:0)-phosphatidylcholine (diC(12:0)PC), respectively, the latter in the presence of 7 M urea. Successful refolding of all variants into both micelles and liposomes ruled out an essential role for the helix or helix-barrel interactions in folding and membrane insertion. Measurements of thermal stability indicated that the variants R59L, W17A/R59L and Delta(1-19) were destabilised substantially compared with wild-type PagP. However, in contrast to the other variants, destabilisation of the W17A variant relative to wild-type PagP was much greater in liposomes than in micelles. Analysis of the kinetics of folding and unfolding of all variants in diC(12:0)PC liposomes suggested that this destabilisation arises predominantly from an increased dissociation of the refolded variant proteins from the lipid-inserted state. The data support the view that the helix of PagP is not required for folding and assembly, but instead acts as a clamp, stabilising membrane-inserted PagP after folding and docking with the membrane are complete.
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Affiliation(s)
- Gerard H.M. Huysmans
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
- Institute of Membrane and Systems Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Sheena E. Radford
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
- Institute of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - David J. Brockwell
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
- Institute of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Stephen A. Baldwin
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
- Institute of Membrane and Systems Biology, University of Leeds, Leeds, LS2 9JT, UK
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44
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Stanley AM, Fleming KG. The role of a hydrogen bonding network in the transmembrane beta-barrel OMPLA. J Mol Biol 2007; 370:912-24. [PMID: 17555765 DOI: 10.1016/j.jmb.2007.05.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Revised: 05/04/2007] [Accepted: 05/06/2007] [Indexed: 11/27/2022]
Abstract
The hydrogen bonding of polar side-chains has emerged as an important theme for membrane protein interactions. The crystal structure of the dimeric state of the transmembrane beta-barrel protein outer membrane phospholipase A (OMPLA) revealed an intermolecular hydrogen bond mediated by a highly conserved glutamine side-chain (Q94). It has been shown that the introduction of a polar residue can drive the association of model helices, and by extension it was presumed that the glutamine hydrogen bond played a key role in stabilizing the OMPLA dimer. However, a thermodynamic investigation using sedimentation equilibrium ultracentrifugation in detergent micelles reveals that the hydrogen bond plays only a very modest role in stabilizing the dimer. The Q94 side-chain is hydrogen bonded intramolecularly to residues Y92 and S96, but amino acid substitutions at these positions suggest these intramolecular interactions are not responsible for attenuating the strength of the intermolecular Q94 hydrogen bond. Other substitutions suggested that hydration of the local environment around Q94 may be responsible for the modest strength of the hydrogen bond. Heat inactivation experiments with the variants suggest that the Y92-Q94-S96 network may instead be important for thermal stability of the monomer. These results highlight the context dependence and broad range of interactions that can be mediated by polar residues in membrane proteins.
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Affiliation(s)
- Ann Marie Stanley
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
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45
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Kortekaas J, Pettersson A, van der Biezen J, Weynants VE, van der Ley P, Poolman J, Bos MP, Tommassen J. Shielding of immunogenic domains in Neisseria meningitidis FrpB (FetA) by the major variable region. Vaccine 2007; 25:72-84. [PMID: 16914236 DOI: 10.1016/j.vaccine.2006.07.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Revised: 07/12/2006] [Accepted: 07/13/2006] [Indexed: 10/24/2022]
Abstract
The meningococcal iron-limitation-inducible outer membrane protein FrpB (FetA) has been shown to induce bactericidal antibodies, and is, therefore, considered a vaccine candidate. However, these antibodies are strain specific and, consistently, epitope mapping showed that they are directed against a region, located in a surface-exposed loop, L5, that displays considerable sequence variability between strains. Here, we attempted to redirect the immune response to more conserved domains of the protein by deleting L5. Immunization with an FrpB protein lacking L5 resulted in a bactericidal antibody response, and epitope mapping showed that these antibodies were directed against loop L3, which also displays considerable sequence variability. To re-direct the immune response further, immunizations were performed with an FrpB protein lacking both L5 and L3. The antibodies obtained were not bactericidal. Furthermore, the bactericidal antibodies against L3 were only bactericidal in the absence of L5, and immunofluorescence microscopy experiments showed that L5 efficiently shields other immunogenic cell surface-exposed epitopes outside of this region on living cells. Whereas the ability of micro-organisms to vary surface-exposed domains that are targets for protective immunity has long been established, the current work shows that such domains can be remarkably efficient in shielding other, more conserved epitopes.
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Affiliation(s)
- Jeroen Kortekaas
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, Padualaan, 3584 CH Utrecht, The Netherlands
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Kortekaas J, Müller SA, Ringler P, Gregorini M, Weynants VE, Rutten L, Bos MP, Tommassen J. Immunogenicity and structural characterisation of an in vitro folded meningococcal siderophore receptor (FrpB, FetA). Microbes Infect 2006; 8:2145-53. [PMID: 16797200 DOI: 10.1016/j.micinf.2006.04.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Revised: 04/03/2006] [Accepted: 04/04/2006] [Indexed: 11/19/2022]
Abstract
The iron-limitation-inducible protein FrpB of Neisseria meningitidis is an outer-membrane-localized siderophore receptor. Because of its abundance and its capacity to elicit bactericidal antibodies, it is considered a vaccine candidate. Bactericidal antibodies against FrpB are, however, type-specific. Hence, an FrpB-based vaccine should comprise several FrpB variants to be capable of providing broad protection. To facilitate the development of a meningococcal subunit vaccine, we have established a procedure to obtain large quantities of the protein in a native-like conformation. The protein was expressed without its signal sequence in Escherichia coli, where it accumulated in inclusion bodies. After in vitro folding, the protein was biochemically, biophysically and biologically characterised. Our results show that in vitro folded FrpB assembles into oligomers, presumably dimers, and that it induces high levels of bactericidal antibodies in laboratory animals.
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Affiliation(s)
- Jeroen Kortekaas
- Department of Molecular Microbiology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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Stanley AM, Chuawong P, Hendrickson TL, Fleming KG. Energetics of outer membrane phospholipase A (OMPLA) dimerization. J Mol Biol 2006; 358:120-31. [PMID: 16497324 DOI: 10.1016/j.jmb.2006.01.033] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2005] [Revised: 01/05/2006] [Accepted: 01/06/2006] [Indexed: 11/29/2022]
Abstract
Outer membrane phospholipase A (OMPLA) is a widely conserved transmembrane enzyme found in Gram-negative bacteria, and it is implicated in the virulence of a number of pathogenic organisms. The regulation of the protein's phospholipase activity is not well understood despite the existence of a number of high resolution structures. Previous biochemical studies have demonstrated that dimerization of OMPLA is a prerequisite for its phospholipase activity, and it has been shown in vitro that this dimerization is dependent on calcium and substrate binding. Therefore, to fully understand the regulation of OMPLA, it is necessary to understand the stability of the protein dimer and the extent to which it is influenced by its effector molecules. We have used sedimentation equilibrium analytical ultracentrifugation to dissect the energetics of Escherichia coli OMPLA dimerization in detergent micelles. We find that calcium contributes relatively little stability to the dimer, while interactions with the substrate acyl chain are the predominant force in stabilizing the dimeric conformation of the enzyme. The resulting thermodynamic cycle suggests that interactions between effector molecules are additive. These energetic measurements not only provide insight into the activation of OMPLA, but they also represent the first quantitative investigation of the association energetics of a transmembrane beta-barrel. This thermodynamic study allows us to begin to address the differences between protein-protein interfaces in transmembrane proteins with a helical fold to those of a beta-barrel fold and to more fully understand the forces involved in membrane protein interactions.
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Affiliation(s)
- Ann Marie Stanley
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
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Mogensen JE, Kleinschmidt JH, Schmidt MA, Otzen DE. Misfolding of a bacterial autotransporter. Protein Sci 2005; 14:2814-27. [PMID: 16199663 PMCID: PMC2253222 DOI: 10.1110/ps.051628705] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Revised: 08/09/2005] [Accepted: 08/15/2005] [Indexed: 10/25/2022]
Abstract
The adhesin involved in diffuse adherence (AIDA) is an autotransporter protein that confers the diffuse adherence phenotype to certain diarrheagenic Escherichia coli strains. It consists of a 49 amino acid signal peptide, a 797 amino acid passenger domain, and a 440 amino acid beta-domain integrated into the outer membrane. The beta-domain consists of two parts: the beta(1)-domain, which is predicted to form two beta-strands on the bacterial cell surface, and the beta(2)-domain, which constitutes the transmembrane domain. We have previously shown that the beta-domain can be folded from the urea-denatured state when bound to a nickel column during purification. It has not been possible to achieve proper refolding of the beta-domain in solution; instead, a misfolded state C is formed. Here, we characterize this misfolded state in greater detail, showing that despite being misfolded, C can be analyzed as a conventional conformational state, with cooperative unfolding in urea and SDS as well as showing simple exponential kinetics during its formation in the presence of lipid vesicles and detergent micelles. The kinetics of formation of C is sensitive to the lipid composition in vesicles. We have also attempted to identify biological factors that might aid folding of the beta-domain to the properly folded state. However, no purified periplasmic or cytosolic chaperone was found to increase folding yields, and no factor in a periplasmic extract was identified that could bind to C. We conclude that it is the exposure to the unique spatial arrangement of the bacterial cell that leads to proper refolding of the beta-domain.
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Affiliation(s)
- Jesper E Mogensen
- Department of Life Sciences, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark
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Wright CS, Mi LZ, Lee S, Rastinejad F. Crystal Structure Analysis of Phosphatidylcholine−GM2-Activator Product Complexes: Evidence for Hydrolase Activity,. Biochemistry 2005; 44:13510-21. [PMID: 16216074 DOI: 10.1021/bi050668w] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
GM2-activator protein (GM2AP) is a lysosomal lipid transfer protein with important biological roles in ganglioside catabolism, phospholipid metabolism, and T-cell activation. Previous studies of crystal structures of GM2AP complexed with the physiological ligand GM2 and platelet activating factor (PAF) have shown binding at two specific locations within the spacious apolar pocket and an ordering effect of endogenous resident lipids. To investigate the structural basis of phospholipid binding further, GM2AP was cocrystallized with phosphatidylcholine (PC), known to interact with GM2AP. Analysis of three crystal forms revealed binding of single chain lipids and fatty acids only and surprisingly not intact PC. The regions of best defined electron density are consistent with the presence of lyso-PC and oleic acid, which constitute deacylation products of PC. Their acyl tails are in stacking contact with shorter, less well-defined stretches of electron density that may represent resident fatty acids. The GM2AP associated hydrolytic activity that generates lyso-PC was further confirmed by mass spectrometry and enzymatic assays. In addition, we report the structures of (i) mutant Y137S, assessing the role of Tyr137 in lipid transfer via the hydrophobic cleft, and (ii) apo-mouse GM2AP, revealing a hydrophobic pocket with a constricted opening. Our structural results provide new insights into the biological functions of GM2AP. The combined effect of hydrolytic and lipid transfer properties has profound implications in cellular signaling.
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Affiliation(s)
- Christine S Wright
- Department of Pharmacology, X-ray Crystallography Laboratory, University of Virginia, Charlottesville, Virginia 22908-0735, USA.
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Bos MP, Tefsen B, Voet P, Weynants V, van Putten JPM, Tommassen J. Function of neisserial outer membrane phospholipase a in autolysis and assessment of its vaccine potential. Infect Immun 2005; 73:2222-31. [PMID: 15784566 PMCID: PMC1087465 DOI: 10.1128/iai.73.4.2222-2231.2005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Outer membrane phospholipase A (OMPLA) is an outer membrane-localized enzyme, present in many gram-negative bacterial species. It is implicated in the virulence of several pathogens. Here, we investigated the presence, function, and vaccine potential of OMPLA in the human pathogen Neisseria meningitidis. Immunoblot analysis showed the presence of OMPLA in 28 out of 33 meningococcal strains investigated. The OMPLA-negative strains all contained a pldA gene, but these alleles contained premature stop codons. All six Neisseria gonorrhoeae strains tested, but only two out of seven commensal neisserial strains investigated, expressed OMPLA, showing that OMPLA is expressed by, but not limited to, many pathogenic neisserial strains. The function of OMPLA was investigated by assessing the phenotypes of isogenic strains, expressing no OMPLA, expressing wild-type levels of OMPLA, or overexpressing OMPLA. OMPLA exhibited phospholipase activity against endogenous phospholipids. Furthermore, OMPLA was characterized as an autolysin that acted under specific conditions, such as prolonged growth of the bacteria. The vaccine potential of the protein was investigated by immunizing mice with in vitro refolded, recombinant OMPLA. High levels of antibody titers were obtained, but the murine sera were neither bactericidal nor protective. Also, convalescent patients and vaccinee sera did not contain detectable levels of anti-OMPLA antibodies, indicating that OMPLA may not be sufficiently immunogenic to be included in a meningococcal vaccine.
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Affiliation(s)
- Martine P Bos
- Department of Molecular Microbiology and Institute for Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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