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Andersen KK, Wang H, Otzen DE. A Kinetic Analysis of the Folding and Unfolding of OmpA in Urea and Guanidinium Chloride: Single and Parallel Pathways. Biochemistry 2012; 51:8371-83. [DOI: 10.1021/bi300974y] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Kell K. Andersen
- Interdisciplinary Nanoscience Centre (iNANO), Centre
for Insoluble Protein Structures (inSPIN), Department of Molecular
Biology and Genetics, University of Aarhus, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark
| | - Huabing Wang
- Interdisciplinary Nanoscience Centre (iNANO), Centre
for Insoluble Protein Structures (inSPIN), Department of Molecular
Biology and Genetics, University of Aarhus, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark
| | - Daniel E. Otzen
- Interdisciplinary Nanoscience Centre (iNANO), Centre
for Insoluble Protein Structures (inSPIN), Department of Molecular
Biology and Genetics, University of Aarhus, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark
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52
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Two outer membrane lipoproteins from Histophilus somni are immunogenic in rabbits and sheep and induce protection against bacterial challenge in mice. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2012; 19:1826-32. [PMID: 22971783 DOI: 10.1128/cvi.00451-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Histophilus somni is an economically important pathogen of cattle and other ruminants and is considered one of the key components of the bovine respiratory disease (BRD) complex, the leading cause of economic loss in the livestock industry. BRD is a multifactorial syndrome, in which a triad of agents, including bacteria, viruses, and predisposing factors or "stressors," combines to induce disease. Although vaccines against H. somni have been used for many decades, traditional bacterins have failed to demonstrate effective protection in vaccinated animals. Hence, the BRD complex continues to produce strong adverse effects on the health and well-being of stock and feeder cattle. The generation of recombinant proteins may facilitate the development of more effective vaccines against H. somni, which could confer better protection against BRD. In the present study, primers were designed to amplify, clone, express, and purify two recombinant lipoproteins from H. somni, p31 (Plp4) and p40 (LppB), which are structural proteins of the outer bacterial membrane. The results presented here demonstrate, to our knowledge for the first time, that when formulated, an experimental vaccine enriched with these two recombinant lipoproteins generates high antibody titers in rabbits and sheep and exerts a protective effect in mice against septicemia induced by H. somni bacterial challenge.
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53
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van de Waterbeemd B, Streefland M, van Keulen L, van den IJssel J, de Haan A, Eppink MH, van der Pol LA. Identification and optimization of critical process parameters for the production of NOMV vaccine against Neisseria meningitidis. Vaccine 2012; 30:3683-90. [DOI: 10.1016/j.vaccine.2012.03.028] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 03/07/2012] [Accepted: 03/12/2012] [Indexed: 11/16/2022]
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54
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Moon DC, Choi CH, Lee JH, Choi CW, Kim HY, Park JS, Kim SI, Lee JC. Acinetobacter baumannii outer membrane protein A modulates the biogenesis of outer membrane vesicles. J Microbiol 2012; 50:155-60. [PMID: 22367951 DOI: 10.1007/s12275-012-1589-4] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 01/16/2012] [Indexed: 02/07/2023]
Abstract
Acinetobacter baumannii secretes outer membrane vesicles (OMVs) during both in vitro and in vivo growth, but the biogenesis mechanism by which A. baumannii produces OMVs remains undefined. Outer membrane protein A of A. baumannii (AbOmpA) is a major protein in the outer membrane and the C-terminus of AbOmpA interacts with diaminopimelate of peptidoglycan. This study investigated the role of AbOmpA in the biogenesis of A. baumannii OMVs. Quantitative and qualitative approaches were used to analyze OMV biogenesis in A. baumannii ATCC 19606T and an isogenic ΔAbOmpA mutant. OMV production was significantly increased in the ΔAbOmpA mutant compared to wild-type bacteria as demonstrated by quantitation of proteins and lipopolysaccharides (LPS) packaged in OMVs. LPS profiles prepared from OMVs from wild-type bacteria and the ΔAbOmpA mutant had identical patterns, but proteomic analysis showed different protein constituents in OMVs from wild-type bacteria compared to the ΔAbOmpA mutant. In conclusion, AbOmpA influences OMV biogenesis by controlling OMV production and protein composition.
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Affiliation(s)
- Dong Chan Moon
- Department of Microbiology, Kyungpook National University School of Medicine, Daegu, 700-422, Republic of Korea
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55
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Sugawara E, Nagano K, Nikaido H. Alternative folding pathways of the major porin OprF of Pseudomonas aeruginosa. FEBS J 2012; 279:910-8. [PMID: 22240095 DOI: 10.1111/j.1742-4658.2012.08481.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OprF is the major porin of Pseudomonas aeruginosa and allows very slow, nonspecific, diffusion of solutes. The low permeability of this porin channel is a major factor that enhances other types of resistance mechanisms and often creates strong multidrug resistance in this nosocomial pathogen. We have previously shown that the low permeability is caused by the folding of OprF into two conformers: a majority, two-domain closed-channel conformer containing the N-terminal transmembrane β-barrel and the C-terminal periplasmic, globular domain; and a minority, one-domain open-channel conformer comprising < 5% of the protein population. Our analysis of the bifurcate folding pathway using site-directed mutagenesis showed that slowing down the folding of the two-domain conformer increases the fraction of the open, one-domain conformer. Use of outer membrane protein assembly machinery mutants showed that the absence of the Skp chaperone led to an increased proportion of open conformers. As many environmental pathogens causing nosocomial infections appear to have outer membrane protein (OmpA)/OprF homologs as the major porin, efforts to understand the low permeability of these 'slow porins' are important in our fight against these organisms.
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Affiliation(s)
- Etsuko Sugawara
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
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56
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Yao Y, Barghava N, Kim J, Niederweis M, Marassi FM. Molecular structure and peptidoglycan recognition of Mycobacterium tuberculosis ArfA (Rv0899). J Mol Biol 2011; 416:208-20. [PMID: 22206986 DOI: 10.1016/j.jmb.2011.12.030] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 10/30/2011] [Accepted: 12/13/2011] [Indexed: 02/03/2023]
Abstract
Mycobacterium tuberculosis ArfA (Rv0899) is a membrane protein encoded by an operon that is required for supporting bacterial growth in acidic environments. Its C-terminal domain (C domain) shares significant sequence homology with the OmpA-like family of peptidoglycan-binding domains, suggesting that its physiological function in acid stress protection may be related to its interaction with the mycobacterial cell wall. Previously, we showed that ArfA forms three independently structured modules, and we reported the structure of its central domain (B domain). Here, we describe the high-resolution structure and dynamics of the C domain, we identify ArfA as a peptidoglycan-binding protein and we elucidate the molecular basis for its specific recognition of diaminopimelate-type peptidoglycan. The C domain of ArfA adopts the characteristic fold of the OmpA-like family. It exhibits pH-dependent conformational dynamics (with significant heterogeneity at neutral pH and a more ordered structure at acidic pH), which could be related to its acid stress response. The C domain associates tightly with polymeric peptidoglycan isolated from M. tuberculosis and also associates with a soluble peptide intermediate of peptidoglycan biosynthesis. This enabled us to characterize the peptidoglycan binding site where five highly conserved ArfA residues, including two key arginines, establish the specificity for diaminopimelate- but not Lys-type peptidoglycan. ArfA is the first peptidoglycan-binding protein to be identified in M. tuberculosis. Its functions in acid stress protection and peptidoglycan binding suggest a link between the acid stress response and the physicochemical properties of the mycobacterial cell wall.
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Affiliation(s)
- Yong Yao
- Sanford Burnham Medical Research Institute, La Jolla, CA 92037, USA
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57
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Park JS, Lee WC, Choi S, Yeo KJ, Song JH, Han YH, Lee JC, Kim SI, Jeon YH, Cheong C, Kim HY. Overexpression, purification, crystallization and preliminary X-ray crystallographic analysis of the periplasmic domain of outer membrane protein A from Acinetobacter baumannii. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:1531-3. [PMID: 22139158 DOI: 10.1107/s1744309111038401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Accepted: 09/19/2011] [Indexed: 11/10/2022]
Abstract
Outer membrane protein A from Acinetobacter baumannii (AbOmpA) is a major outer membrane protein and a key player in the bacterial pathogenesis that induces host cell death. AbOmpA is presumed to consist of an N-terminal β-barrel transmembrane domain and a C-terminal periplasmic OmpA-like domain. In this study, the recombinant C-terminal periplasmic domain of AbOmpA was overexpressed in Escherichia coli, purified and crystallized using the vapour-diffusion method. A native diffraction data set was collected to a resolution of 2.0 Å using synchrotron radiation. The space group of the crystal was P2(1), with unit-cell parameters a = 58.24, b = 98.59, c = 97.96 Å, β = 105.92°. The native crystal contained seven or eight molecules per asymmetric unit and had a calculated Matthews coefficient of 2.93 or 2.56 Å(3) Da(-1).
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Affiliation(s)
- Jeong Soon Park
- Division of Magnetic Resonance, Korea Basic Science Institute, Ochang, Chungbuk, Republic of Korea
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58
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Li J, Shi C, Gao Y, Wu K, Shi P, Lai C, Chen L, Wu F, Tian C. Structural studies of Mycobacterium tuberculosis Rv0899 reveal a monomeric membrane-anchoring protein with two separate domains. J Mol Biol 2011; 415:382-92. [PMID: 22108166 DOI: 10.1016/j.jmb.2011.11.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2011] [Revised: 11/02/2011] [Accepted: 11/08/2011] [Indexed: 11/26/2022]
Abstract
Rv0899 from Mycobacterium tuberculosis belongs to the OmpA (outer membrane protein A) family of outer membrane proteins. It functions as a pore-forming protein; the deletion of this gene impairs the uptake of some water-soluble substances, such as serine, glucose, and glycerol. Rv0899 has also been shown to play a part in low-pH environment adaption, which may play a part in pathogenic mycobacteria overcoming the host's defense mechanisms. Based on many bacterial physiological data and recent structural studies, it was proposed that Rv0899 forms an oligomeric channel to carry out such functions. In this work, biochemical and structural data obtained from solution NMR and EPR spectroscopy indicated that Rv0899 is a monomeric membrane-anchoring protein with two separate domains, rather than an oligomeric pore. Using NMR chemical shift perturbation and isothermal calorimetric titration assays, we show that Rv0899 was able to interact with Zn(2+) ions, which may indicate a role for Rv0899 in the process of Zn(2+) acquisition.
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Affiliation(s)
- Juan Li
- Hefei National Laboratory for Physical Science at Microscale and School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, China
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59
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Yung-Hung RL, Ismail A, Lim TS, Choong YS. A 35kDa antigenic protein from Shigella flexneri: In silico structural and functional studies. Biochem Biophys Res Commun 2011; 415:229-34. [DOI: 10.1016/j.bbrc.2011.09.116] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 09/23/2011] [Indexed: 11/27/2022]
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60
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Park JS, Lee WC, Yeo KJ, Ryu KS, Kumarasiri M, Hesek D, Lee M, Mobashery S, Song JH, Kim SI, Lee JC, Cheong C, Jeon YH, Kim HY. Mechanism of anchoring of OmpA protein to the cell wall peptidoglycan of the gram-negative bacterial outer membrane. FASEB J 2011; 26:219-28. [PMID: 21965596 DOI: 10.1096/fj.11-188425] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The outer membrane protein A (OmpA) plays important roles in anchoring of the outer membrane to the bacterial cell wall. The C-terminal periplasmic domain of OmpA (OmpA-like domain) associates with the peptidoglycan (PGN) layer noncovalently. However, there is a paucity of information on the structural aspects of the mechanism of PGN recognition by OmpA-like domains. To elucidate this molecular recognition process, we solved the high-resolution crystal structure of an OmpA-like domain from Acinetobacter baumannii bound to diaminopimelate (DAP), a unique bacterial amino acid from the PGN. The structure clearly illustrates that two absolutely conserved Asp271 and Arg286 residues are the key to the binding to DAP of PGN. Identification of DAP as the central anchoring site of PGN to OmpA is further supported by isothermal titration calorimetry and a pulldown assay with PGN. An NMR-based computational model for complexation between the PGN and OmpA emerged, and this model is validated by determining the crystal structure in complex with a synthetic PGN fragment. These structural data provide a detailed glimpse of how the anchoring of OmpA to the cell wall of gram-negative bacteria takes place in a DAP-dependent manner.
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Affiliation(s)
- Jeong Soon Park
- Division of Magnetic Resonance Research, Korea Basic Science Institute, Chungbuk, Korea
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61
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Marassi FM. Mycobacterium tuberculosis Rv0899 defines a family of membrane proteins widespread in nitrogen-fixing bacteria. Proteins 2011; 79:2946-55. [PMID: 21905117 DOI: 10.1002/prot.23151] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/30/2011] [Accepted: 07/21/2011] [Indexed: 11/07/2022]
Abstract
The Mycobacterium tuberculosis membrane protein Rv0899 confers adaptation of the bacterium to acidic environments. Due to strong sequence homology of its C-terminus to bacterial OmpA-like domains, Rv0899 has been proposed to constitute an outer membrane porin of M. tuberculosis. However, OmpA-like domains are widespread in a wide variety of bacterial proteins with different functions. Furthermore, the three-dimensional structure of Rv0899 does not contain a transmembrane β-barrel, and recent evidence demonstrates that it does not have porin activity. Instead, the rv0899 gene is part of an operon (rv0899-rv0901) that is required for fast ammonia secretion, pH neutralization, and growth of M. tuberculosis in acidic environments. The mechanism whereby these functions are accomplished is not known. To gain further functional insights, a targeted search of the genomic databases was performed for proteins with sequence similarity beyond the OmpA-like C-terminus. The results presented here, show that Rv0899-like proteins are widespread in bacteria with functions in nitrogen metabolism, adaptation to nutrient poor environments, and/or establishing symbiosis with the host organism, and appear to form a protein family. These findings suggest that M. tuberculosis Rv0899 may also assist similar processes and lend further support to its role in ammonia secretion and M. tuberculosis adaptation to the host environment.
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Affiliation(s)
- Francesca M Marassi
- Sanford Burnham Medical Research Institute, La Jolla, California 92037, USA.
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62
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The soluble, periplasmic domain of OmpA folds as an independent unit and displays chaperone activity by reducing the self-association propensity of the unfolded OmpA transmembrane β-barrel. Biophys Chem 2011; 159:194-204. [PMID: 21782315 DOI: 10.1016/j.bpc.2011.06.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Revised: 06/13/2011] [Accepted: 06/20/2011] [Indexed: 11/22/2022]
Abstract
OmpA is one of only a few transmembrane proteins whose folding and stability have been investigated in detail. However, only half of the OmpA mass encodes its transmembrane β-barrel; the remaining sequence is a soluble domain that is localized to the periplasmic side of the outer membrane. To understand how the OmpA periplasmic domain contributes to the stability and folding of the full-length OmpA protein, we cloned, expressed, purified and studied the OmpA periplasmic domain independently of the OmpA transmembrane β-barrel region. Our experiments showed that the OmpA periplasmic domain exists as an independent folding unit with a free energy of folding equal to -6.2 (±0.1) kcal mol(-1) at 25°C. Using circular dichroism, we determined that the OmpA periplasmic domain adopts a mixed alpha/beta secondary structure, a conformation that has previously been used to describe the partially folded non-native state of the full-length OmpA. We further discovered that the OmpA periplasmic domain reduces the self-association propensity of the unfolded barrel domain, but only when covalently attached (in cis). In vitro folding experiments showed that self-association competes with β-barrel folding when allowed to occur before the addition of membranes, and the periplasmic domain enhances the folding efficiency of the full-length protein by reducing its self-association. These results identify a novel chaperone function for the periplasmic domain of OmpA that may be relevant for folding in vivo. We have also extensively investigated the properties of the self-association reaction of unfolded OmpA and found that the transmembrane region must form a critical nucleus comprised of three molecules before undergoing further oligomerization to form large molecular weight species. Finally, we studied the conformation of the unfolded OmpA monomer and found that the folding-competent form of the transmembrane region adopts an expanded conformation, which is in contrast to previous studies that have suggested a collapsed unfolded state.
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63
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Oliveira R, de Morais ZM, Gonçales AP, Romero EC, Vasconcellos SA, Nascimento ALTO. Characterization of novel OmpA-like protein of Leptospira interrogans that binds extracellular matrix molecules and plasminogen. PLoS One 2011; 6:e21962. [PMID: 21755014 PMCID: PMC3130794 DOI: 10.1371/journal.pone.0021962] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Accepted: 06/15/2011] [Indexed: 11/30/2022] Open
Abstract
Leptospira interrogans is the etiological agent of leptospirosis, a zoonotic disease of human and veterinary concern. The identification of novel proteins that mediate host-pathogen interactions is important for understanding the bacterial pathogenesis as well as to identify protective antigens that would help fight the disease. We describe in this work the cloning, expression, purification and characterization of three predicted leptospiral membrane proteins, LIC10258, LIC12880 (Lp30) and LIC12238. We have employed Escherichia coli BL21 (SI) strain as a host expression system. Recently, we have identified LIC12238 as a plasminogen (PLG)-binding receptor. We show now that Lp30 and rLIC10258 are also PLG-receptors of Leptospira, both exhibiting dose-dependent and saturating binding (K(D), 68.8±25.2 nM and 167.39±60.1 nM, for rLIC10258 and rLIC12880, respectively). In addition, LIC10258, which is a novel OmpA-like protein, binds laminin and plasma fibronectin ECM molecules and hence, it was named Lsa66 (Leptospiral surface adhesin of 66 kDa). Binding of Lsa66 to ECM components was determined to be specific, dose-dependent and saturable, with a K(D) of 55.4±15.9 nM to laminin and of 290.8±11.8 nM to plasma fibronectin. Binding of the recombinant proteins to PLG or ECM components was assessed by using antibodies against each of the recombinant proteins obtained in mice and confirmed by monoclonal anti-polyhistidine antibodies. Lsa66 caused partial inhibition on leptospiral adherence to immobilized ECM and PLG. Moreover, this adhesin and rLIC12238 are recognized by antibodies in serum samples of confirmed leptospirosis cases. Thus, Lsa66 is a novel OmpA-like protein with dual activity that may promote the attachment of Leptospira to host tissues and may contribute to the leptospiral invasion. To our knowledge, this is the first leptospiral protein with ECM and PLG binding properties reported to date.
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Affiliation(s)
- Rosane Oliveira
- Centro de Biotecnologia, Instituto Butantan, São Paulo, Brazil
- Interunidades em Biotecnologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Zenaide Maria de Morais
- Laboratório de Zoonoses Bacterianas do VPS, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, Brazil
| | - Amane Paldes Gonçales
- Laboratório de Zoonoses Bacterianas do VPS, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, Brazil
| | | | - Silvio Arruda Vasconcellos
- Laboratório de Zoonoses Bacterianas do VPS, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, Brazil
| | - Ana L. T. O. Nascimento
- Centro de Biotecnologia, Instituto Butantan, São Paulo, Brazil
- Interunidades em Biotecnologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
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64
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Zheng C, Yang L, Hoopmann MR, Eng JK, Tang X, Weisbrod CR, Bruce JE. Cross-linking measurements of in vivo protein complex topologies. Mol Cell Proteomics 2011; 10:M110.006841. [PMID: 21697552 DOI: 10.1074/mcp.m110.006841] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Identification and measurement of in vivo protein interactions pose critical challenges in the goal to understand biological systems. The measurement of structures and topologies of proteins and protein complexes as they exist in cells is particularly challenging, yet critically important to improve understanding of biological function because proteins exert their intended function only through the structures and interactions they exhibit in vivo. In the present study, protein interactions in E. coli cells were identified in our unbiased cross-linking approach, yielding the first in vivo topological data on many interactions and the largest set of identified in vivo cross-linked peptides produced to date. These data show excellent agreement with protein and complex crystal structures where available. Furthermore, our unbiased data provide novel in vivo topological information that can impact understanding of biological function, even for cases where high resolution structures are not yet available.
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Affiliation(s)
- Chunxiang Zheng
- Department of Chemistry, Washington State University, Pullman, WA 99164, USA
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65
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Structure of the flagellar motor protein complex PomAB: implications for the torque-generating conformation. J Bacteriol 2011; 193:3863-70. [PMID: 21642461 DOI: 10.1128/jb.05021-11] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The bacterial flagellar motor is driven by an ion flux through a channel called MotAB in Escherichia coli or Salmonella and PomAB in Vibrio alginolyticus. PomAB is composed of two transmembrane (TM) components, PomA and PomB, and converts a sodium ion flux to rotation of the flagellum. Its homolog, MotAB, utilizes protons instead of sodium ions. PomB/MotB has a peptidoglycan (PG)-binding motif in the periplasmic domain, allowing it to function as the stator by being anchored to the PG layer. To generate torque, PomAB/MotAB is thought to undergo a conformational change triggered by the ion flux and to interact directly with FliG, a component of the rotor. Here, we present the first three-dimensional structure of this torque-generating stator unit analyzed by electron microscopy. The structure of PomAB revealed two arm domains, which contain the PG-binding site, connected to a large base made of the TM and cytoplasmic domains. The arms lean downward to the membrane surface, likely representing a "plugged" conformation, which would prevent ions leaking through the channel. We propose a model for how PomAB units are placed around the flagellar basal body to function as torque generators.
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66
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Rexroth S, Mullineaux CW, Ellinger D, Sendtko E, Rögner M, Koenig F. The plasma membrane of the cyanobacterium Gloeobacter violaceus contains segregated bioenergetic domains. THE PLANT CELL 2011; 23:2379-90. [PMID: 21642550 PMCID: PMC3160022 DOI: 10.1105/tpc.111.085779] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Revised: 04/01/2011] [Accepted: 05/14/2011] [Indexed: 05/18/2023]
Abstract
The light reactions of oxygenic photosynthesis almost invariably take place in the thylakoid membranes, a highly specialized internal membrane system located in the stroma of chloroplasts and the cytoplasm of cyanobacteria. The only known exception is the primordial cyanobacterium Gloeobacter violaceus, which evolved before the appearance of thylakoids and harbors the photosynthetic complexes in the plasma membrane. Thus, studies on G. violaceus not only shed light on the evolutionary origin and the functional advantages of thylakoid membranes but also might include insights regarding thylakoid formation during chloroplast differentiation. Based on biochemical isolation and direct in vivo characterization, we report here structural and functional domains in the cytoplasmic membrane of a cyanobacterium. Although G. violaceus has no internal membranes, it does have localized domains with apparently specialized functions in its plasma membrane, in which both the photosynthetic and the respiratory complexes are concentrated. These bioenergetic domains can be visualized by confocal microscopy, and they can be isolated by a simple procedure. Proteomic analysis of these domains indicates their physiological function and suggests a protein sorting mechanism via interaction with membrane-intrinsic terpenoids. Based on these results, we propose specialized domains in the plasma membrane as evolutionary precursors of thylakoids.
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Affiliation(s)
- Sascha Rexroth
- Plant Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany.
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67
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Yang Y, Auguin D, Delbecq S, Dumas E, Molle G, Molle V, Roumestand C, Saint N. Structure of the Mycobacterium tuberculosis OmpATb protein: a model of an oligomeric channel in the mycobacterial cell wall. Proteins 2011; 79:645-61. [PMID: 21117233 DOI: 10.1002/prot.22912] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The pore-forming outer membrane protein OmpATb from Mycobacterium tuberculosis is a virulence factor required for acid resistance in host phagosomes. In this study, we determined the 3D structure of OmpATb by NMR in solution. We found that OmpATb is composed of two independent domains separated by a proline-rich hinge region. As expected, the high-resolution structure of the C-terminal domain (OmpATb(198-326)) revealed a module structurally related to other OmpA-like proteins from Gram-negative bacteria. The N-terminal domain of OmpATb (73-204), which is sufficient to form channels in planar lipid bilayers, exhibits a fold, which belongs to the α+β sandwich class fold. Its peculiarity is to be composed of two overlapping subdomains linked via a BON (Bacterial OsmY and Nodulation) domain initially identified in bacterial proteins predicted to interact with phospholipids. Although OmpATb(73-204) is highly water soluble, current-voltage measurements demonstrate that it is able to form conducting pores in model membranes. A HADDOCK modeling of the NMR data gathered on the major monomeric form and on the minor oligomeric populations of OmpATb(73-204) suggest that OmpATb(73-204) can form oligomeric rings able to insert into phospholipid membrane, similar to related proteins from the Type III secretion systems, which form multisubunits membrane-associated rings at the basal body of the secretion machinery.
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Affiliation(s)
- Yinshan Yang
- Centre de Biochimie Structurale, CNRS UMR 5048, Université Montpellier 1 et 2, F34090 Montpellier, France
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Manchur MA, Kikumoto M, Kanao T, Takada J, Kamimura K. Characterization of an OmpA-like outer membrane protein of the acidophilic iron-oxidizing bacterium, Acidithiobacillus ferrooxidans. Extremophiles 2011; 15:403-10. [PMID: 21472537 PMCID: PMC3084935 DOI: 10.1007/s00792-011-0371-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 03/23/2011] [Indexed: 11/27/2022]
Abstract
An OmpA family protein (FopA) previously reported as one of the major outer membrane proteins of an acidophilic iron-oxidizing bacterium Acidithiobacillus ferrooxidans was characterized with emphasis on the modification by heat and the interaction with peptidoglycan. A 30-kDa band corresponding to the FopA protein was detected in outer membrane proteins extracted at 75°C or heated to 100°C for 10 min prior to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). However, the band was not detected in outer membrane proteins extracted at ≤40°C and without boiling prior to electrophoresis. By Western blot analysis using the polyclonal antibody against the recombinant FopA, FopA was detected as bands with apparent molecular masses of 30 and 90 kDa, suggesting that FopA existed as an oligomeric form in the outer membrane of A. ferrooxidans. Although the fopA gene with a sequence encoding the signal peptide was successfully expressed in the outer membrane of Escherichia coli, the recombinant FopA existed as a monomer in the outer membrane of E. coli. FopA was detected in peptidoglycan-associated proteins from A. ferrooxidans. The recombinant FopA also showed the peptidoglycan-binding activity.
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Affiliation(s)
- Mohammed Abul Manchur
- Division of Bioscience, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-Naka, Okayama, 700-8530, Japan
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69
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Scheurwater EM, Burrows LL. Maintaining network security: how macromolecular structures cross the peptidoglycan layer. FEMS Microbiol Lett 2011; 318:1-9. [DOI: 10.1111/j.1574-6968.2011.02228.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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70
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Factors affecting the folding of Pseudomonas aeruginosa OprF porin into the one-domain open conformer. mBio 2010; 1. [PMID: 20978537 PMCID: PMC2957080 DOI: 10.1128/mbio.00228-10] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 09/17/2010] [Indexed: 11/30/2022] Open
Abstract
Pseudomonas aeruginosa OprF is a largely monomeric outer membrane protein that allows the slow, nonspecific transmembrane diffusion of solutes. This protein folds into two different conformers, with the majority conformer folding into a two-domain conformation that has no porin activity and the minority conformer into a one-domain conformation with high porin activity and presumably consisting of a large β barrel. We examined the factors that control the divergent folding pathways of OprF. OprF contains four Cys residues in the linker region connecting the N-terminal β-barrel domain and the C-terminal globular domain in the majority conformer. Prevention of disulfide bond formation either by expression of OprF in an Escherichia coli dsbA strain grown with dithiothreitol or by replacement of all Cys residues with serine (CS OprF) increased the specific pore-forming activity of OprF significantly. Replacement of Phe160 with Ile at the end of the β-barrel termination signal as well as replacement of Lys164 in the linker region with Gly, Cys, or Glu increased porin activity 2-fold. Improving a potential β-barrel termination signal in the periplasmic domain by replacement of Asp211 with asparagine also increased porin activity. The porin activity could be improved about 5-fold by the combination of these replacements. OprF mutants with higher porin activity were shown to contain more one-domain conformers by surface labeling of the A312C residue in intact cells, as this residue is located in the periplasmic domain in the two-domain conformers. Finally, when the OprF protein was expressed in an E. coli strain lacking the periplasmic chaperone Skp, the CS OprF protein exhibited increased pore-forming activity. High intrinsic levels of resistance to many antimicrobial agents, seen in Gram-negative bacterial species such as Pseudomonas aeruginosa and Acinetobacter species, are largely due to the extremely low permeability of their major porin OprF and OmpA. Because this low permeability is caused by the fact that these proteins mostly fold into a two-domain conformer without pores, knowledge as to what conditions increase the production of the pore-forming minority conformer may lead to dramatic improvements in the treatment of infections by these bacteria. We have found several factors that increase the proportion of the pore-forming conformer up to 5-fold. Although these studies were done with Escherichia coli, they may serve as the starting point for the design of strategies for improvement of antimicrobial therapy for these difficult-to-treat pathogens, some strains of which have now attained the “pan-resistant” status.
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71
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Bakolitsa C, Kumar A, Jin KK, McMullan D, Krishna SS, Miller MD, Abdubek P, Acosta C, Astakhova T, Axelrod HL, Burra P, Carlton D, Chen C, Chiu HJ, Clayton T, Das D, Deller MC, Duan L, Elias Y, Ellrott K, Ernst D, Farr CL, Feuerhelm J, Grant JC, Grzechnik A, Grzechnik SK, Han GW, Jaroszewski L, Johnson HA, Klock HE, Knuth MW, Kozbial P, Marciano D, Morse AT, Murphy KD, Nigoghossian E, Nopakun A, Okach L, Paulsen J, Puckett C, Reyes R, Rife CL, Sefcovic N, Tien HJ, Trame CB, Trout CV, van den Bedem H, Weekes D, White A, Xu Q, Hodgson KO, Wooley J, Elsliger MA, Deacon AM, Godzik A, Lesley SA, Wilson IA. Structures of the first representatives of Pfam family PF06684 (DUF1185) reveal a novel variant of the Bacillus chorismate mutase fold and suggest a role in amino-acid metabolism. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:1182-9. [PMID: 20944209 PMCID: PMC2954203 DOI: 10.1107/s1744309109050647] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Accepted: 11/24/2009] [Indexed: 11/17/2022]
Abstract
The crystal structures of BB2672 and SPO0826 were determined to resolutions of 1.7 and 2.1 Å by single-wavelength anomalous dispersion and multiple-wavelength anomalous dispersion, respectively, using the semi-automated high-throughput pipeline of the Joint Center for Structural Genomics (JCSG) as part of the NIGMS Protein Structure Initiative (PSI). These proteins are the first structural representatives of the PF06684 (DUF1185) Pfam family. Structural analysis revealed that both structures adopt a variant of the Bacillus chorismate mutase fold (BCM). The biological unit of both proteins is a hexamer and analysis of homologs indicates that the oligomer interface residues are highly conserved. The conformation of the critical regions for oligomerization appears to be dependent on pH or salt concentration, suggesting that this protein might be subject to environmental regulation. Structural similarities to BCM and genome-context analysis suggest a function in amino-acid synthesis.
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Affiliation(s)
- Constantina Bakolitsa
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
| | - Abhinav Kumar
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Kevin K. Jin
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Daniel McMullan
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - S. Sri Krishna
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Mitchell D. Miller
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Polat Abdubek
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Claire Acosta
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Tamara Astakhova
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Herbert L. Axelrod
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Prasad Burra
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
| | - Dennis Carlton
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Connie Chen
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Hsiu-Ju Chiu
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Thomas Clayton
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Debanu Das
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Marc C. Deller
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Lian Duan
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Ylva Elias
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Kyle Ellrott
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- University of California, San Diego, La Jolla, CA, USA
| | - Dustin Ernst
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Carol L. Farr
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Julie Feuerhelm
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Joanna C. Grant
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Anna Grzechnik
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Slawomir K. Grzechnik
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Gye Won Han
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Lukasz Jaroszewski
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Hope A. Johnson
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Heath E. Klock
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Mark W. Knuth
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Piotr Kozbial
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
| | - David Marciano
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Andrew T. Morse
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Kevin D. Murphy
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Edward Nigoghossian
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Amanda Nopakun
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Linda Okach
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Jessica Paulsen
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Christina Puckett
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Ron Reyes
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Christopher L. Rife
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Natasha Sefcovic
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
| | - Henry J. Tien
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Christine B. Trame
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Christina V. Trout
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Henry van den Bedem
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Dana Weekes
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
| | - Aprilfawn White
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Qingping Xu
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Keith O. Hodgson
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Photon Science, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - John Wooley
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Marc-Andre Elsliger
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Ashley M. Deacon
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Adam Godzik
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Program on Bioinformatics and Systems Biology, Burnham Institute for Medical Research, La Jolla, CA, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA, USA
| | - Scott A. Lesley
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, CA, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Ian A. Wilson
- Joint Center for Structural Genomics, http://www.jcsg.org, USA
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA
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72
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Aschtgen MS, Gavioli M, Dessen A, Lloubès R, Cascales E. The SciZ protein anchors the enteroaggregative Escherichia coli Type VI secretion system to the cell wall. Mol Microbiol 2010; 75:886-99. [PMID: 20487285 DOI: 10.1111/j.1365-2958.2009.07028.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Type VI secretion systems (T6SS) are multi-component machines encoded within the genomes of most Gram-negative bacteria that associate with plant, animal and/or human cells, and therefore are considered as potential virulence factors. We recently launched a study on the Sci-1 T6SS of enteroaggregative Escherichia coli (EAEC). The Sci-1 T6SS is composed of all or a subset of the 21 gene products encoded within the cluster, 13 of which are shared by all T6SS identified so far. In the present work, we focussed our attention on the SciZ protein. We first showed that SciZ is required for the release of the Hcp protein in the culture supernatant and for efficient biofilm formation, demonstrating that SciZ is necessary for EAEC T6SS function. Indeed, SciZ forms a complex with SciP, SciS and SciN, three core components of the transport apparatus. Fractionation and topology studies showed that SciZ is a polytopic inner membrane protein with three trans-membrane segments. Computer analyses identified a motif shared by peptidoglycan binding proteins of the OmpA family in the SciZ periplasmic domain. Using in vivo and in vitro binding assays, we showed that this motif anchors the SciZ protein to the cell wall and is required for T6SS function.
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Affiliation(s)
- Marie-Stéphanie Aschtgen
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Université de la Méditerranée - Aix-Marseille II, CNRS - UPR 9027, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
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73
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Tracing phylogenomic events leading to diversity of Haemophilus influenzae and the emergence of Brazilian Purpuric Fever (BPF)-associated clones. Genomics 2010; 96:290-302. [PMID: 20654709 DOI: 10.1016/j.ygeno.2010.07.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2010] [Revised: 07/12/2010] [Accepted: 07/14/2010] [Indexed: 11/22/2022]
Abstract
Here we report the use of a multi-genome DNA microarray to elucidate the genomic events associated with the emergence of the clonal variants of Haemophilus influenzae biogroup aegyptius causing Brazilian Purpuric Fever (BPF), an important pediatric disease with a high mortality rate. We performed directed genome sequencing of strain HK1212 unique loci to construct a species DNA microarray. Comparative genome hybridization using this microarray enabled us to determine and compare gene complements, and infer reliable phylogenomic relationships among members of the species. The higher genomic variability observed in the genomes of BPF-related strains (clones) and their close relatives may be characterized by significant gene flux related to a subset of functional role categories. We found that the acquisition of a large number of virulence determinants featuring numerous cell membrane proteins coupled to the loss of genes involved in transport, central biosynthetic pathways and in particular, energy production pathways to be characteristics of the BPF genomic variants.
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74
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van de Waterbeemd B, Streefland M, van der Ley P, Zomer B, van Dijken H, Martens D, Wijffels R, van der Pol L. Improved OMV vaccine against Neisseria meningitidis using genetically engineered strains and a detergent-free purification process. Vaccine 2010; 28:4810-6. [DOI: 10.1016/j.vaccine.2010.04.082] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Revised: 04/26/2010] [Accepted: 04/27/2010] [Indexed: 11/25/2022]
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75
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Teriete P, Yao Y, Kolodzik A, Yu J, Song H, Niederweis M, Marassi FM. Mycobacterium tuberculosis Rv0899 adopts a mixed alpha/beta-structure and does not form a transmembrane beta-barrel. Biochemistry 2010; 49:2768-77. [PMID: 20199110 DOI: 10.1021/bi100158s] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The membrane protein Rv0899 (OmpATb) from Mycobacterium tuberculosis, has been proposed to act as an outer membrane porin and to contribute to the bacterium's adaptation to the acidic environment of the phagosome during infection. The gene is restricted to pathogenic mycobacteria and, thus, is an attractive candidate for the development of anti-tuberculosis chemotherapy. The 326-residue protein contains three domains: an N-terminal domain (residues 1-72) that includes a sequence of 20 hydrophobic amino acids required for membrane translocation, a central B domain (residues 73-200) with homology to the conserved putative lipid-binding BON (bacterial OsmY and nodulation) superfamily, and a C domain (residues 201-326) with homology to the OmpA-C-like superfamily of periplasmic peptidoglycan-binding sequences, found in several types of bacterial membrane proteins, including in the C-terminus of the Escherichia coli outer membrane protein OmpA. We have characterized the structure and dynamics of the B and C domains and have determined the three-dimensional structure of the B domain. Rv0899 does not form a transmembrane beta-barrel. Residues 73-326 form a mixed alpha/beta-globular structure, encompassing two independently folded modules corresponding to the B and C domains connected by a flexible linker. The B domain folds with three parallel/antiparallel alpha-helices packed against six parallel/antiparallel beta-strands that form a flat beta-sheet. The core is hydrophobic, while the exterior is polar and predominantly acidic. The structure of a BON homology domain is revealed here for the first time. In light of this unexpected structure, it is hard to reconcile an outer membrane porin activity with the central domain of the protein. The structure of the B domain and the overall architecture of the protein suggest alternative modes of membrane association.
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Affiliation(s)
- Peter Teriete
- Sanford Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, California 92037, USA
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76
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Ryan KR, Taylor JA, Bowers LM. The BAM complex subunit BamE (SmpA) is required for membrane integrity, stalk growth and normal levels of outer membrane {beta}-barrel proteins in Caulobacter crescentus. MICROBIOLOGY (READING, ENGLAND) 2010; 156:742-756. [PMID: 19959579 PMCID: PMC2889432 DOI: 10.1099/mic.0.035055-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 11/20/2009] [Accepted: 11/27/2009] [Indexed: 11/18/2022]
Abstract
The outer membrane of Gram-negative bacteria is an essential compartment containing a specific complement of lipids and proteins that constitute a protective, selective permeability barrier. Outer membrane beta-barrel proteins are assembled into the membrane by the essential hetero-oligomeric BAM complex, which contains the lipoprotein BamE. We have identified a homologue of BamE, encoded by CC1365, which is located in the outer membrane of the stalked alpha-proteobacterium Caulobacter crescentus. BamE associates with proteins whose homologues in other bacteria are known to participate in outer membrane protein assembly: BamA (CC1915), BamB (CC1653) and BamD (CC1984). Caulobacter cells lacking BamE grow slowly in rich medium and are hypersensitive to anionic detergents, some antibiotics and heat exposure, which suggest that the membrane integrity of the mutant is compromised. Membranes of the DeltabamE mutant have normal amounts of the outer membrane protein RsaF, a TolC homologue, but are deficient in CpaC*, an aggregated form of the outer membrane secretin for type IV pili. Delta bamE membranes also contain greatly reduced amounts of three TonB-dependent receptors that are abundant in wild-type cells. Cells lacking BamE have short stalks and are delayed in stalk outgrowth during the cell cycle. Based on these findings, we propose that Caulobacter BamE participates in the assembly of outer membrane beta-barrel proteins, including one or more substrates required for the initiation of stalk biogenesis.
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Affiliation(s)
- Kathleen R Ryan
- Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, Berkeley, CA 94720, USA
| | - James A Taylor
- Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Lisa M Bowers
- Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, Berkeley, CA 94720, USA
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77
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Yan W, Faisal SM, McDonough SP, Chang CF, Pan MJ, Akey B, Chang YF. Identification and characterization of OmpA-like proteins as novel vaccine candidates for Leptospirosis. Vaccine 2010; 28:2277-83. [DOI: 10.1016/j.vaccine.2009.12.071] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Revised: 12/23/2009] [Accepted: 12/29/2009] [Indexed: 11/28/2022]
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78
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A modular BAM complex in the outer membrane of the alpha-proteobacterium Caulobacter crescentus. PLoS One 2010; 5:e8619. [PMID: 20062535 PMCID: PMC2797634 DOI: 10.1371/journal.pone.0008619] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Accepted: 12/11/2009] [Indexed: 11/19/2022] Open
Abstract
Mitochondria are organelles derived from an intracellular α-proteobacterium. The biogenesis of mitochondria relies on the assembly of β-barrel proteins into the mitochondrial outer membrane, a process inherited from the bacterial ancestor. Caulobacter crescentus is an α-proteobacterium, and the BAM (β-barrel assembly machinery) complex was purified and characterized from this model organism. Like the mitochondrial sorting and assembly machinery complex, we find the BAM complex to be modular in nature. A ∼150 kDa core BAM complex containing BamA, BamB, BamD, and BamE associates with additional modules in the outer membrane. One of these modules, Pal, is a lipoprotein that provides a means for anchorage to the peptidoglycan layer of the cell wall. We suggest the modular design of the BAM complex facilitates access to substrates from the protein translocase in the inner membrane.
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79
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Volokhina EB, Beckers F, Tommassen J, Bos MP. The beta-barrel outer membrane protein assembly complex of Neisseria meningitidis. J Bacteriol 2009; 191:7074-85. [PMID: 19767435 PMCID: PMC2772484 DOI: 10.1128/jb.00737-09] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2009] [Accepted: 09/09/2009] [Indexed: 11/20/2022] Open
Abstract
The evolutionarily conserved protein Omp85 is required for outer membrane protein (OMP) assembly in gram-negative bacteria and in mitochondria. Its Escherichia coli homolog, designated BamA, functions with four accessory lipoproteins, BamB, BamC, BamD, and BamE, together forming the beta-barrel assembly machinery (Bam). Here, we addressed the composition of this machinery and the function of its components in Neisseria meningitidis, a model organism for outer membrane biogenesis studies. Analysis of genome sequences revealed homologs of BamC, BamD (previously described as ComL), and BamE and a second BamE homolog, Mlp. No homolog of BamB was found. As in E. coli, ComL/BamD appeared essential for viability and for OMP assembly, and it could not be replaced by its E. coli homolog. BamE was not essential but was found to contribute to the efficiency of OMP assembly and to the maintenance of OM integrity. A bamC mutant showed only marginal OMP assembly defects, but the impossibility of creating a bamC bamE double mutant further indicated the function of BamC in OMP assembly. An mlp mutant was unaffected in OMP assembly. The results of copurification assays demonstrated the association of BamC, ComL, and BamE with Omp85. Semi-native gel electrophoresis identified the RmpM protein as an additional component of the Omp85 complex, which was confirmed in copurification assays. RmpM was not required for OMP folding but stabilized OMP complexes. Thus, the Bam complex in N. meningitidis consists of Omp85/BamA plus RmpM, BamC, ComL/BamD, and BamE, of which ComL/BamD and BamE appear to be the most important accessory components for OMP assembly.
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Affiliation(s)
- Elena B. Volokhina
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Frank Beckers
- 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
| | - Martine P. Bos
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands
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80
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Hara Y, Mohamed R, Nathan S. Immunogenic Burkholderia pseudomallei outer membrane proteins as potential candidate vaccine targets. PLoS One 2009; 4:e6496. [PMID: 19654871 PMCID: PMC2716516 DOI: 10.1371/journal.pone.0006496] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 07/01/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Burkholderia pseudomallei is the causative agent of melioidosis, a disease of significant morbidity and mortality in both human and animals in endemic areas. There is no vaccine towards the bacterium available in the market, and the efficacy of many of the bacterium's surface and secreted proteins are currently being evaluated as vaccine candidates. METHODOLOGY/PRINCIPAL FINDINGS With the availability of the B. pseudomallei whole genome sequence, we undertook to identify genes encoding the known immunogenic outer membrane protein A (OmpA). Twelve OmpA domains were identified and ORFs containing these domains were fully annotated. Of the 12 ORFs, two of these OmpAs, Omp3 and Omp7, were successfully cloned, expressed as soluble protein and purified. Both proteins were recognised by antibodies in melioidosis patients' sera by Western blot analysis. Purified soluble fractions of Omp3 and Omp7 were assessed for their ability to protect BALB/c mice against B. pseudomallei infection. Mice were immunised with either Omp3 or Omp7, subsequently challenged with 1x10(6) colony forming units (cfu) of B. pseudomallei via the intraperitoneal route, and examined daily for 21 days post-challenge. This pilot study has demonstrated that whilst all control unimmunised mice died by day 9 post-challenge, two mice (out of 4) from both immunised groups survived beyond 21 days post-infection. CONCLUSIONS/SIGNIFICANCE We have demonstrated that B. pseudomallei OmpA proteins are immunogenic in mice as well as melioidosis patients and should be further assessed as potential vaccine candidates against B. pseudomallei infection.
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Affiliation(s)
- Yuka Hara
- Malaysia Genome Institute, UKM-MTDC Smart Technology Centre, Bangi, Selangor, Malaysia
| | - Rahmah Mohamed
- Malaysia Genome Institute, UKM-MTDC Smart Technology Centre, Bangi, Selangor, Malaysia
- School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia
| | - Sheila Nathan
- Malaysia Genome Institute, UKM-MTDC Smart Technology Centre, Bangi, Selangor, Malaysia
- School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia
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81
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Kojima S, Imada K, Sakuma M, Sudo Y, Kojima C, Minamino T, Homma M, Namba K. Stator assembly and activation mechanism of the flagellar motor by the periplasmic region of MotB. Mol Microbiol 2009; 73:710-8. [PMID: 19627504 DOI: 10.1111/j.1365-2958.2009.06802.x] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Torque generation in the Salmonella flagellar motor is coupled to translocation of H(+) ions through the proton-conducting channel of the Mot protein stator complex. The Mot complex is believed to be anchored to the peptidoglycan (PG) layer by the putative peptidoglycan-binding (PGB) domain of MotB. Proton translocation is activated only when the stator is installed into the motor. We report the crystal structure of a C-terminal periplasmic fragment of MotB (MotB(C)) that contains the PGB domain and includes the entire periplasmic region essential for motility. Structural and functional analyses indicate that the PGB domains must dimerize in order to form the proton-conducting channel. Drastic conformational changes in the N-terminal portion of MotB(C) are required both for PG binding and the proton channel activation.
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Affiliation(s)
- Seiji Kojima
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-Ku, Nagoya 464-8602, Japan
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82
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Hizukuri Y, Morton JF, Yakushi T, Kojima S, Homma M. The peptidoglycan-binding (PGB) domain of the Escherichia coli pal protein can also function as the PGB domain in E. coli flagellar motor protein MotB. J Biochem 2009; 146:219-29. [PMID: 19364805 DOI: 10.1093/jb/mvp061] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The bacterial flagellar stator proteins, MotA and MotB, form a complex and are thought to be anchored to the peptidoglycan by the C-terminal conserved peptidoglycan-binding (PGB) motif of MotB. To clarify the role of the C-terminal region, we performed systematic cysteine mutagenesis and constructed a chimeric MotB protein which was replaced with the peptidoglycan-associated lipoprotein Pal. Although this chimera could not restore motility to a motB strain, we were able to isolate two motile revertants. One was F172V in the Pal region and the other was P159L in the MotB region. Furthermore, we attempted to map the MotB Cys mutations in the crystal structure of Escherichia coli Pal. We found that the MotB mutations that affected motility nearly overlapped with the predicted PG-binding residues of Pal. Our results indicate that, although the functions of MotB and Pal are very different, the PGB region of Pal is interchangeable with the PGB region of MotB.
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83
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Horton RE, Vidarsson G, Virji M, Williams NA, Heyderman RS. IgA1 antibodies specific for outer membrane protein PorA modulate the interaction between Neisseria meningitidis and the epithelium. Microb Pathog 2009; 46:253-60. [PMID: 19486642 DOI: 10.1016/j.micpath.2009.01.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2008] [Revised: 12/18/2008] [Accepted: 01/29/2009] [Indexed: 01/23/2023]
Abstract
Despite high carriage rates of Neisseria meningitidis, incidence of meningococcal disease remains low, partially due to development of natural immunity. We have previously demonstrated an inverse relationship between salivary anti-meningococcal IgA and disease incidence, but little is known about the contribution of IgA to immunity at mucosal surfaces. Here we show strong immunoreactivity by human salivary IgA against the meningococcal outer membrane porin, PorA. Monomeric anti-PorA IgA1 (humanized chimeric antibodies) but not IgG increased the association of unencapsulated serogroup B N. meningitidis (H44/76) with Chang (conjunctival) but not with either Detroit (pharyngeal) cells or with A549 (alveolar) epithelial cells. Association of encapsulated N. meningitidis was not increased. Epithelial binding of IgA was Fc fragment dependent and not inhibited by IgM. Together these data suggest the presence of a specific epithelial IgA receptor that could influence the effect of both naturally acquired and vaccine induced IgA antibodies at the epithelial surface.
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Affiliation(s)
- R E Horton
- Department of Cellular and Molecular Medicine, School of Medical Sciences, University of Bristol, Bristol, UK.
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84
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The cavity-chaperone Skp protects its substrate from aggregation but allows independent folding of substrate domains. Proc Natl Acad Sci U S A 2009; 106:1772-7. [PMID: 19181847 DOI: 10.1073/pnas.0809275106] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Outer membrane proteins (OMPs) of gram-negative bacteria are synthesized in the cytosol and must cross the periplasm before insertion into the outer membrane. The 17-kDa protein (Skp) is a periplasmic chaperone that assists the folding and insertion of many OMPs, including OmpA, a model OMP with a membrane embedded beta-barrel domain and a periplasmic alphabeta domain. Structurally, Skp belongs to a family of cavity-containing chaperones that bind their substrates in the cavity, protecting them from aggregation. However, some substrates, such as OmpA, exceed the capacity of the chaperone cavity, posing a mechanistic challenge. Here, we provide direct NMR evidence that, while bound to Skp, the beta-barrel domain of OmpA is maintained in an unfolded state, whereas the periplasmic domain is folded in its native conformation. Complementary cross-linking and NMR relaxation experiments show that the OmpA beta-barrel is bound deep within the Skp cavity, whereas the folded periplasmic domain protrudes outside of the cavity where it tumbles independently from the rest of the complex. This domain-based chaperoning mechanism allows the transport of beta-barrels across the periplasm in an unfolded state, which may be important for efficient insertion into the outer membrane.
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85
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Crystal structure of the cell wall anchor domain of MotB, a stator component of the bacterial flagellar motor: implications for peptidoglycan recognition. Proc Natl Acad Sci U S A 2008; 105:10348-53. [PMID: 18647830 DOI: 10.1073/pnas.0803039105] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The stator ring of the bacterial flagellar motor is composed of the MotA and MotB proteins that act together to generate a turning force (torque) acting on the FliG ring of the rotor. The C-terminal domain of MotB (MotB-C) is believed to anchor the MotA/MotB complex to peptidoglycan (PG) of the cell wall. The first crystal structures of MotB-C and its complex with N-acetylmuramic acid (NAM) have been determined to 1.6- and 2.3-A resolution, respectively. MotB-C is a dimer, both in solution and in the crystal. The two glycan chains of the PG ligand can be modeled as semirigid helices and docked into the grooves harboring the NAM molecules on the opposite faces of the dimer. The model suggests that a concave hydrophilic surface created upon edge-to-edge beta-sheet dimerization and centered around the 2-fold axis of the dimer can accommodate the peptide cross-bridge linking the two sugar chains. Significant structural similarities were found between MotB-C and the PG-binding domains of reduction-modifiable protein M and peptidoglycan-associated lipoprotein exclude, suggesting that PG recognition by different outer membrane protein A-like proteins may be governed by very similar molecular mechanisms that evidently involve protein dimerization.
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86
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Candidate stress genes of Nitrosomonas europaea for monitoring inhibition of nitrification by heavy metals. Appl Environ Microbiol 2008; 74:5475-82. [PMID: 18606795 DOI: 10.1128/aem.00500-08] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Heavy metals have been shown to be strong inhibitors of nitrification in wastewater treatment plants. In this research, the effects of cadmium, copper, and mercury on Nitrosomonas europaea were studied in quasi-steady-state batch reactors. When cells were exposed to 1 microM CdCl2, 6 microM HgCl2, or 8 microM CuCl2, ammonia oxidation rates were decreased by about 90%. Whole-genome transcriptional and proteomic responses of N. europaea to cadmium were used to identify heavy metal stress response genes. When cells were exposed to 1 microM CdCl2 for 1 h, 66 genes (of the total of 2,460 genes) were upregulated, and 50 genes were downregulated more than twofold. Of these, the mercury resistance genes (merTPCADE) averaged 277-fold upregulation under 1 microM CdCl2, with merA (mercuric reductase) showing 297-fold upregulation. In N. europaea cells exposed to 6 microM HgCl2 or to 8 microM CuCl2, merA showed 250-fold and 1.7-fold upregulation, respectively. Cells showed the ability to recover quickly from Hg2+-related toxic effects, apparently associated with upregulation of the mercury resistance genes and amoA, but no such recovery was evident in Cd2+-exposed cells even though merTPCADE were highly upregulated. We suggest that the upregulation of merA in response to CdCl2 and HgCl2 exposure may provide a means to develop an early-warning indicator for inhibition of nitrification by these metals.
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87
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Insights into the stator assembly of the Vibrio flagellar motor from the crystal structure of MotY. Proc Natl Acad Sci U S A 2008; 105:7696-701. [PMID: 18505842 DOI: 10.1073/pnas.0800308105] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Rotation of the sodium-driven polar flagellum of Vibrio alginolyticus requires four motor proteins: PomA, PomB, MotX, and MotY. PomA and PomB form a sodium-ion channel in the cytoplasmic membrane that functions as a stator complex to couple sodium-ion flux with torque generation. MotX and MotY are components of the T-ring, which is located beneath the P-ring of the polar flagellar basal body and is involved in incorporation of the PomA/PomB complex into the motor. Here, we describe the determination of the crystal structure of MotY at 2.9 A resolution. The structure shows two distinct domains: an N-terminal domain (MotY-N) and a C-terminal domain (MotY-C). MotY-N has a unique structure. MotY-C contains a putative peptidoglycan-binding motif that is remarkably similar to those of peptidoglycan-binding proteins, such as Pal and RmpM, but this region is disordered in MotY. Motility assay of cells producing either of the MotY-N and MotY-C fragments and subsequent biochemical analyses indicate that MotY-N is essential for association of the stator units around the rotor, whereas MotY-C stabilizes the association by binding to the peptidoglycan layer. Based on these observations, we propose a model for the mechanism of stator assembly around the rotor.
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88
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Roujeinikova A. Cloning, purification and preliminary X-ray analysis of the C-terminal domain of Helicobacter pylori MotB. Acta Crystallogr Sect F Struct Biol Cryst Commun 2008; 64:277-80. [PMID: 18391426 PMCID: PMC2374257 DOI: 10.1107/s1744309108005277] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Accepted: 02/25/2008] [Indexed: 11/10/2022]
Abstract
The C-terminal domain of MotB (MotB-C) contains a putative peptidoglycan-binding motif and is believed to anchor the MotA/MotB stator unit of the bacterial flagellar motor to the cell wall. Crystals of Helicobacter pylori MotB-C (138 amino-acid residues) were obtained by the hanging-drop vapour-diffusion method using polyethylene glycol as a precipitant. These crystals belong to space group P2(1), with unit-cell parameters a = 50.8, b = 89.5, c = 66.3 A, beta = 112.5 degrees . The crystals diffract X-rays to at least 1.6 A resolution using a synchrotron-radiation source. Self-rotation function and Matthews coefficient calculations suggest that the asymmetric unit contains one tetramer with 222 point-group symmetry. The anomalous difference Patterson maps calculated for an ytterbium-derivative crystal using diffraction data at a wavelength of 1.38 A showed significant peaks on the v = 1/2 Harker section, suggesting that ab initio phase information could be derived from the MAD data.
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Affiliation(s)
- Anna Roujeinikova
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, England.
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89
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Koyama K, Suzuki H, Noguchi T, Akimoto S, Tsuchiya T, Mimuro M. Oxygen evolution in the thylakoid-lacking cyanobacterium Gloeobacter violaceus PCC 7421. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:369-78. [DOI: 10.1016/j.bbabio.2008.01.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2007] [Revised: 01/24/2008] [Accepted: 01/25/2008] [Indexed: 10/22/2022]
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90
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Characterization of the periplasmic domain of MotB and implications for its role in the stator assembly of the bacterial flagellar motor. J Bacteriol 2008; 190:3314-22. [PMID: 18310339 DOI: 10.1128/jb.01710-07] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
MotA and MotB are integral membrane proteins that form the stator complex of the proton-driven bacterial flagellar motor. The stator complex functions as a proton channel and couples proton flow with torque generation. The stator must be anchored to an appropriate place on the motor, and this is believed to occur through a putative peptidoglycan-binding (PGB) motif within the C-terminal periplasmic domain of MotB. In this study, we constructed and characterized an N-terminally truncated variant of Salmonella enterica serovar Typhimurium MotB consisting of residues 78 through 309 (MotB(C)). MotB(C) significantly inhibited the motility of wild-type cells when exported into the periplasm. Some point mutations in the PGB motif enhanced the motility inhibition, while an in-frame deletion variant, MotB(C)(Delta197-210), showed a significantly reduced inhibitory effect. Wild-type MotB(C) and its point mutant variants formed a stable homodimer, while the deletion variant was monomeric. A small amount of MotB was coisolated only with the secreted form of MotB(C)-His(6) by Ni-nitrilotriacetic acid affinity chromatography, suggesting that the motility inhibition results from MotB-MotB(C) heterodimer formation in the periplasm. However, the monomeric mutant variant MotB(C)(Delta197-210) did not bind to MotB, suggesting that MotB(C) is directly involved in stator assembly. We propose that the MotB(C) dimer domain plays an important role in targeting and stable anchoring of the MotA/MotB complex to putative stator-binding sites of the motor.
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91
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Carpenter T, Khalid S, Sansom MSP. A multidomain outer membrane protein from Pasteurella multocida: Modelling and simulation studies of PmOmpA. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2831-40. [PMID: 17888868 DOI: 10.1016/j.bbamem.2007.07.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Revised: 07/06/2007] [Accepted: 07/26/2007] [Indexed: 10/22/2022]
Abstract
PmOmpA is a two-domain outer membrane protein from Pasteurella multocida. The N-terminal domain of PmOmpA is a homologue of the transmembrane beta-barrel domain of OmpA from Escherichia coli, whilst the C-terminal domain of PmOmpA is a homologue of the extra-membrane Neisseria meningitidis RmpM C-terminal domain. This enables a model of a complete two domain PmOmpA to be constructed and its conformational dynamics explored via MD simulations of the protein embedded within two different phospholipid bilayers (DMPC and DMPE). The conformational stability of the transmembrane beta-barrel is similar to that of a homology model of OprF from Pseudomonas aeruginosa in bilayer simulations. There is a degree of water penetration into the interior of the beta-barrel, suggestive of a possible transmembrane pore. Although the PmOmpA model is stable over 20 ns simulations, retaining its secondary structure and fold integrity throughout, substantial flexibility is observed in a short linker region between the N- and the C-terminal domains. At low ionic strength, the C-terminal domain moves to interact electrostatically with the lipid bilayer headgroups. This study demonstrates that computational approaches may be applied to more complex, multi-domain outer membrane proteins, rather than just to transmembrane beta-barrels, opening the possibility of in silico proteomics approaches to such proteins.
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92
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Engelhardt H. Are S-layers exoskeletons? The basic function of protein surface layers revisited. J Struct Biol 2007; 160:115-24. [PMID: 17889557 DOI: 10.1016/j.jsb.2007.08.003] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 07/29/2007] [Accepted: 08/02/2007] [Indexed: 11/28/2022]
Abstract
Surface protein or glycoprotein layers (S-layers) are common structures of the prokaryotic cell envelope. They are either associated with the peptidoglycan or outer membrane of bacteria, and constitute the only cell wall component of many archaea. Despite their occurrence in most of the phylogenetic branches of microorganisms, the functional significance of S-layers is assumed to be specific for genera or groups of organisms in the same environment rather than common to all prokaryotes. Functional aspects have usually been investigated with isolated S-layer sheets or proteins, which disregards the interactions between S-layers and the underlying cell envelope components. This study discusses the synergistic effects in cell envelope assemblies, the hypothetical role of S-layers for cell shape formation, and the existence of a common function in view of new insights.
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Affiliation(s)
- Harald Engelhardt
- Abteilung Molekulare Strukturbiologie, Max-Planck-Institut für Biochemie, Am Klopferspitz 18, D-82152 Martinsried, Germany.
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93
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Serino L, Nesta B, Leuzzi R, Fontana MR, Monaci E, Mocca BT, Cartocci E, Masignani V, Jerse AE, Rappuoli R, Pizza M. Identification of a new OmpA-like protein in Neisseria gonorrhoeae involved in the binding to human epithelial cells and in vivo colonization. Mol Microbiol 2007; 64:1391-403. [PMID: 17542928 DOI: 10.1111/j.1365-2958.2007.05745.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Outer membrane protein As (OmpAs) are highly conserved proteins within the Enterobacteriaceae family. OmpA contributes to the maintenance of structural membrane integrity and invasion into mammalian cells. In Escherichia coli K1 OmpA also contributes to serum resistance and is involved in the virulence of the bacterium. Here we describe the identification of an OmpA-like protein in Neisseria gonorrhoeae (Ng-OmpA). We show that the gonococcal OmpA-like protein, similarly to E. coli OmpA, plays a significant role in the adhesion and invasion into human cervical carcinoma and endometrial cells and is required for entry into macrophages and intracellular survival. Furthermore, the isogenic knockout ompA mutant demonstrates reduced recovery in a mouse model of infection when compared with the wild-type strain, suggesting that Ng-OmpA plays an important role in the in vivo colonization. All together, these data suggest that the newly identified surface exposed protein Ng-OmpA represents a novel virulence factor of gonococcus.
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Affiliation(s)
- Laura Serino
- Research Centre, Novartis Vaccines, Via Fiorentina, 1, 53100 Siena, Italy.
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94
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Ristow P, Bourhy P, McBride FWDC, Figueira CP, Huerre M, Ave P, Girons IS, Ko AI, Picardeau M. The OmpA-like protein Loa22 is essential for leptospiral virulence. PLoS Pathog 2007; 3:e97. [PMID: 17630832 PMCID: PMC1914066 DOI: 10.1371/journal.ppat.0030097] [Citation(s) in RCA: 160] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2007] [Accepted: 05/17/2007] [Indexed: 11/28/2022] Open
Abstract
Pathogenic mechanisms of Leptospira interrogans, the causal agent of leptospirosis, remain largely unknown. This is mainly due to the lack of tools for genetic manipulations of pathogenic species. In this study, we characterized a mutant obtained by insertion of the transposon Himar1 into a gene encoding a putative lipoprotein, Loa22, which has a predicted OmpA domain based on sequence identity. The resulting mutant did not express Loa22 and was attenuated in virulence in the guinea pig and hamster models of leptospirosis, whereas the genetically complemented strain was restored in Loa22 expression and virulence. Our results show that Loa22 was expressed during host infection and exposed on the cell surface. Loa22 is therefore necessary for virulence of L. interrogans in the animal model and represents, to our knowledge, the first genetically defined virulence factor in Leptospira species.
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Affiliation(s)
- Paula Ristow
- Unité de Biologie des Spirochètes, Institut Pasteur, Paris, France
- Instituto de Microbiologia Professor Paulo de Goes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Pascale Bourhy
- Unité de Biologie des Spirochètes, Institut Pasteur, Paris, France
| | | | | | - Michel Huerre
- Unité de Recherche et d'Expertise Histotechnologie et Pathologie, Institut Pasteur, Paris, France
| | - Patrick Ave
- Unité de Recherche et d'Expertise Histotechnologie et Pathologie, Institut Pasteur, Paris, France
| | | | - Albert I Ko
- Instituto de Microbiologia Professor Paulo de Goes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Division of International Medicine and Infectious Disease, Weill Medical College of Cornell University, New York, New York, United States of America
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95
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Khalid S, Bond PJ, Carpenter T, Sansom MSP. OmpA: gating and dynamics via molecular dynamics simulations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:1871-80. [PMID: 17601489 DOI: 10.1016/j.bbamem.2007.05.024] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2007] [Revised: 05/23/2007] [Accepted: 05/25/2007] [Indexed: 10/23/2022]
Abstract
Outer membrane proteins (OMPs) of Gram-negative bacteria have a variety of functions including passive transport, active transport, catalysis, pathogenesis and signal transduction. Whilst the structures of approximately 25 OMPs are currently known, there is relatively little known about their dynamics in different environments. The outer membrane protein, OmpA from Escherichia coli has been studied extensively in different environments both experimentally and computationally, and thus provides an ideal test case for the study of the dynamics and environmental interactions of outer membrane proteins. We review molecular dynamics simulations of OmpA and its homologues in a variety of different environments and discuss possible mechanisms of pore gating. The transmembrane domain of E. coli OmpA shows subtle differences in dynamics and interactions between a detergent micelle and a lipid bilayer environment. Simulations of the crystallographic unit cell reveal a micelle-like network of detergent molecules interacting with the protein monomers. Simulation and modelling studies emphasise the role of an electrostatic-switch mechanism in the pore-gating mechanism. Simulation studies have been extended to comparative models of OmpA homologues from Pseudomonas aeruginosa (OprF) and Pasteurella multocida (PmOmpA), the latter model including the periplasmic C-terminal domain.
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Affiliation(s)
- Syma Khalid
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
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96
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Akimana C, Lafontaine ER. The Moraxella catarrhalis outer membrane protein CD contains two distinct domains specifying adherence to human lung cells. FEMS Microbiol Lett 2007; 271:12-9. [PMID: 17391370 DOI: 10.1111/j.1574-6968.2007.00693.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Most Moraxella catarrhalis isolates express a highly-conserved outer membrane protein of 453 residues designated OMPCD, which has been previously shown to mediate binding to A549 human lung cells. Here, it is reported that two distinct domains of the M. catarrhalis strain O35E OMPCD protein specify adherence. Truncated proteins were expressed in Escherichia coli to demonstrate that OMPCD residues 1-240 as well as 241-400 are important for attachment to A549 cells, and database searches indicated that amino acids 285-299 resemble an adhesive motif found in eukaryotic proteins termed thrombospondin-type 3 repeat (TT3R). Cellular enzyme-linked immunosorbent assay using His-tagged proteins demonstrated that residues 236-300 of OMPCD, containing the TT3R motif, specify adhesive properties. Furthermore, these assays revealed that a purified protein encompassing residues 16-236 binds to A549 cells. The two cell-binding domains of OMPCD were further defined to amino acids 16-150 and 261-300 by utilizing a surface-display system, which was constructed from the M. catarrhalis autotransporter protein McaP, to express foreign peptides on the surface of recombinant bacteria.
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Affiliation(s)
- Christine Akimana
- Department of Medical Microbiology and Immunology, University of Toledo Health Sciences Campus, Toledo, OH, USA
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97
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Shinohara A, Sakuma M, Yakushi T, Kojima S, Namba K, Homma M, Imada K. Crystallization and preliminary X-ray analysis of MotY, a stator component of the Vibrio alginolyticus polar flagellar motor. Acta Crystallogr Sect F Struct Biol Cryst Commun 2007; 63:89-92. [PMID: 17277446 PMCID: PMC2330118 DOI: 10.1107/s1744309106055850] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2006] [Accepted: 12/22/2006] [Indexed: 11/10/2022]
Abstract
The polar flagellum of Vibrio alginolyticus is rotated by the sodium motor. The stator unit of the sodium motor consists of four different proteins: PomA, PomB, MotX and MotY. MotX and MotY, which are unique components of the sodium motor, form the T-ring structure attached to the LP ring in the periplasmic space. MotY has a putative peptidoglycan-binding motif in its C-terminal region and MotX is suggested to interact with PomB. Thus, MotX and MotY are thought to be required for incorporation and stabilization of the PomA/B complex. In this study, mature MotY composed of 272 amino-acid residues and its SeMet derivative were expressed with a C-terminal hexahistidine-tag sequence, purified and crystallized. Native crystals were grown in the hexagonal space group P6(1)22/P6(5)22, with unit-cell parameters a = b = 104.1, c = 132.6 A. SeMet-derivative crystals belonged to the same space group with the same unit-cell parameters as the native crystals. Anomalous difference Patterson maps of the SeMet derivative showed significant peaks in their Harker sections, indicating that the derivatives are suitable for structure determination.
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Affiliation(s)
- Akari Shinohara
- Soft Nano-Machine Project, CREST, JST, Chikusa-ku, Nagoya 464-8602, Japan
| | - Mayuko Sakuma
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Toshiharu Yakushi
- Soft Nano-Machine Project, CREST, JST, Chikusa-ku, Nagoya 464-8602, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Seiji Kojima
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
- Dynamic NanoMachine Project, ICORP, JST, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Michio Homma
- Soft Nano-Machine Project, CREST, JST, Chikusa-ku, Nagoya 464-8602, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Katsumi Imada
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
- Dynamic NanoMachine Project, ICORP, JST, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
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98
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Durant L, Metais A, Soulama-Mouze C, Genevard JM, Nassif X, Escaich S. Identification of candidates for a subunit vaccine against extraintestinal pathogenic Escherichia coli. Infect Immun 2006; 75:1916-25. [PMID: 17145948 PMCID: PMC1865706 DOI: 10.1128/iai.01269-06] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Extraintestinal pathogenic Escherichia coli (ExPEC) strains cause a large spectrum of infections. The majority of ExPEC strains are closely related to the B2 or the D phylogenetic group. The aim of our study was to develop a protein-based vaccine against these ExPEC strains. To this end, we identified ExPEC-specific genomic regions, using a comparative genome analysis, between the nonpathogenic E. coli strain K-12 MG1655 and ExPEC strains C5 (meningitis isolate) and CFT073 (urinary tract infection isolate). The analysis of these genomic regions allowed the selection of 40 open reading frames, which are conserved among B2/D clinical isolates and encode proteins with putative outer membrane localization. These genes were cloned, and recombinant proteins were purified and assessed as vaccine candidates. After immunization of BALB/c mice, five proteins induced a significant protective immunity against a lethal challenge with a clinical E. coli strain of the B2 group. In passive immunization assays, antigen-specific antibodies afforded protection to naive mice against a lethal challenge. Three of these antigens were related to iron acquisition metabolism, an important virulence factor of the ExPEC, and two corresponded to new, uncharacterized proteins. Due to the large number of genetic differences that exists between commensal and pathogenic strains of E. coli, our results demonstrate that it is possible to identify targets that elicit protective immune responses specific to those strains. The five protective antigens could constitute the basis for a preventive subunit vaccine against diseases caused by ExPEC strains.
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Affiliation(s)
- Lionel Durant
- Mutabilis SA, 102 route de Noisy, 93230 Romainville, France
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99
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Molle V, Saint N, Campagna S, Kremer L, Lea E, Draper P, Molle G. pH-dependent pore-forming activity of OmpATb from Mycobacterium tuberculosis and characterization of the channel by peptidic dissection. Mol Microbiol 2006; 61:826-37. [PMID: 16803587 DOI: 10.1111/j.1365-2958.2006.05277.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mycobacteria are characterized by an unusual cell wall that controls nutrient and small hydrophilic compound permeability. Porin-like proteins are necessary to ensure the transport of molecules into the cell. Here, we investigated the pore-forming properties of OmpATb, a porin from Mycobacterium tuberculosis, in lipid bilayers. Multi-channel experiments showed an asymmetric behaviour with channel closures at negative critical voltages (Vc) and a strong decrease in Vc at acidic pH. Single-channel experiments gave conductance values of about 850 +/- 80 pS in 1 M KCl and displayed a weak cationic selectivity in 4-8 pH range. The production and characterization of a series of truncated OmpATb proteins, showed that the central domain (OmpATb73-220) was sufficient to induce the ion channel properties of the native protein in lipid bilayers, i.e. asymmetric insertion, pH-dependent voltage closure, cationic selectivity and similar conductance values in 1 M KCl. Western blot analysis suggests that the presence of OmpATb is only restricted to certain pathogenic species. Therefore, the propensity of channels of native OmpATb to close at low pH may represent an intrinsic property allowing pathogenic mycobacteria to adapt and survive to mildly acidic conditions, such as those encountered within the macrophage phagosome.
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Affiliation(s)
- Virginie Molle
- IBCP, UMR 5086 CNRS, University of Lyon, 69367 Lyon, France
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100
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Zakharian E, Reusch RN. Pore characteristics of nontypeable Haemophilus influenzae outer membrane protein P5 in planar lipid bilayers. Biophys J 2006; 91:3242-8. [PMID: 16905616 PMCID: PMC1614495 DOI: 10.1529/biophysj.106.088781] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The structure of outer membrane protein P5 of NTHi, a homolog of Escherichia coli OmpA, was investigated by observing its pore characteristics in planar lipid bilayers. Recombinant NTHi P5 was overexpressed in E. coli and purified using ionic detergent, LDS-P5, or nonionic detergent, OG-P5. LDS-P5 and OG-P5 could not be distinguished by their migration on SDS-PAGE gels; however, when incorporated into planar bilayers of DPhPC between symmetric aqueous solutions of 1 M KCl at 22 degrees C, LDS-P5 formed narrow pores (58 +/- 6 pS) with low open probability, whereas OG-P5 formed large pores (1.1 +/- 0.1 nS) with high open probability (0.99). LDS-P5 narrow pores were gradually and irreversibly transformed into large pores, indistinguishable from those formed by OG-P5, at temperatures >or=40 degrees C; the process took 4-6 h at 40 degrees C or 35-45 min at 42 degrees C. Large pores were stable to changes in temperatures; however, large pores were rapidly converted to narrow pores when exposed to LDS at room temperatures, indicating acute sensitivity of this conformer to ionic detergent. These studies suggest that narrow pores are partially denatured forms and support the premise that the native conformation of NTHi P5 is that of a large monomeric pore.
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Affiliation(s)
- E Zakharian
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, 48824, USA
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