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Crane JM, Randall LL. The Sec System: Protein Export in Escherichia coli. EcoSal Plus 2017; 7:10.1128/ecosalplus.ESP-0002-2017. [PMID: 29165233 PMCID: PMC5807066 DOI: 10.1128/ecosalplus.esp-0002-2017] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Indexed: 11/20/2022]
Abstract
In Escherichia coli, proteins found in the periplasm or the outer membrane are exported from the cytoplasm by the general secretory, Sec, system before they acquire stably folded structure. This dynamic process involves intricate interactions among cytoplasmic and membrane proteins, both peripheral and integral, as well as lipids. In vivo, both ATP hydrolysis and proton motive force are required. Here, we review the Sec system from the inception of the field through early 2016, including biochemical, genetic, and structural data.
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Affiliation(s)
- Jennine M. Crane
- Department of Biochemistry, University of Missouri, Columbia, Missouri
| | - Linda L. Randall
- Department of Biochemistry, University of Missouri, Columbia, Missouri
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2
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Zhou Q, Sun S, Tai P, Sui SF. Structural characterization of the complex of SecB and metallothionein-labeled proOmpA by cryo-electron microscopy. PLoS One 2012; 7:e47015. [PMID: 23056562 PMCID: PMC3464278 DOI: 10.1371/journal.pone.0047015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 09/11/2012] [Indexed: 11/19/2022] Open
Abstract
ProOmpA is a preprotein that is translocated across the plasma membrane by the general secretory pathway in Escherichia coli. The molecular chaperon SecB in Sec pathway can recognize and bind proOmpA for its translocation. However, the structure of the SecB/proOmpA complex remains unknown. Here, we constructed an uncleavable proOmpA fused with metallothionein at its C-terminus and labeled it with metals in vitro for the study of cryo-electron microscopy. Using single particle cryo-electron microscopy, we reconstructed 3D structure of the stable SecB/proOmpA complex. The structure shows that the major portion of preprotein locates on one side of SecB tetramer, resulting in an asymmetric binding pattern. This work also provides a possible approach to the structure determination of small protein complexes by cryo-electron microscopy.
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Affiliation(s)
- Qiang Zhou
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Shan Sun
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Phang Tai
- Department of Biology, Georgia State University, Atlanta, Georgia, United States of America
| | - Sen-Fang Sui
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
- * E-mail:
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3
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Tang Y, Pan X, Tai PC, Sui SF. The structure of SecB/OmpA as visualized by electron microscopy: The mature region of the precursor protein binds asymmetrically to SecB. Biochem Biophys Res Commun 2010; 393:698-702. [PMID: 20170640 DOI: 10.1016/j.bbrc.2010.02.062] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Accepted: 02/11/2010] [Indexed: 10/19/2022]
Abstract
SecB, a molecular chaperone in Escherichia coli, binds a subset of precursor proteins that are exported across the plasma membrane via the Sec pathway. Previous studies showed that SecB bound directly to the mature region rather than to the signal sequence of the precursor protein. To determine the binding pattern of SecB and the mature region of the preprotein, here, we visualized the structure of the SecB/OmpA complex by electron microscopy. This complex is composed by two parts: the main density represents one SecB tetramer and the unfolded part of OmpA wrapping round it; the elongated smaller density represents the rest of OmpA. Each SecB protomer makes a different contribution to the binding of SecB with OmpA. The binding pattern between SecB tetramer and OmpA is asymmetric.
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Affiliation(s)
- Ying Tang
- State-Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Structural Biology, School of Life Science, Tsinghua University, Beijing 100084, China
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4
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Gatsos X, Perry AJ, Anwari K, Dolezal P, Wolynec PP, Likić VA, Purcell AW, Buchanan SK, Lithgow T. Protein secretion and outer membrane assembly in Alphaproteobacteria. FEMS Microbiol Rev 2008; 32:995-1009. [PMID: 18759741 PMCID: PMC2635482 DOI: 10.1111/j.1574-6976.2008.00130.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Revised: 06/23/2008] [Accepted: 07/18/2008] [Indexed: 11/17/2022] Open
Abstract
The assembly of beta-barrel proteins into membranes is a fundamental process that is essential in Gram-negative bacteria, mitochondria and plastids. Our understanding of the mechanism of beta-barrel assembly is progressing from studies carried out in Escherichia coli and Neisseria meningitidis. Comparative sequence analysis suggests that while many components mediating beta-barrel protein assembly are conserved in all groups of bacteria with outer membranes, some components are notably absent. The Alphaproteobacteria in particular seem prone to gene loss and show the presence or absence of specific components mediating the assembly of beta-barrels: some components of the pathway appear to be missing from whole groups of bacteria (e.g. Skp, YfgL and NlpB), other proteins are conserved but are missing characteristic domains (e.g. SurA). This comparative analysis is also revealing important structural signatures that are vague unless multiple members from a protein family are considered as a group (e.g. tetratricopeptide repeat (TPR) motifs in YfiO, beta-propeller signatures in YfgL). Given that the process of the beta-barrel assembly is conserved, analysis of outer membrane biogenesis in Alphaproteobacteria, the bacterial group that gave rise to mitochondria, also promises insight into the assembly of beta-barrel proteins in eukaryotes.
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Affiliation(s)
- Xenia Gatsos
- Department of Biochemistry and Molecular Biology, University of MelbourneMelbourne, Australia
- Bio21 Molecular Science and Biotechnology Institute, University of MelbourneMelbourne, Australia
| | - Andrew J Perry
- Department of Biochemistry and Molecular Biology, University of MelbourneMelbourne, Australia
- Bio21 Molecular Science and Biotechnology Institute, University of MelbourneMelbourne, Australia
| | - Khatira Anwari
- Department of Biochemistry and Molecular Biology, University of MelbourneMelbourne, Australia
- Bio21 Molecular Science and Biotechnology Institute, University of MelbourneMelbourne, Australia
| | - Pavel Dolezal
- Department of Biochemistry and Molecular Biology, University of MelbourneMelbourne, Australia
- Bio21 Molecular Science and Biotechnology Institute, University of MelbourneMelbourne, Australia
| | - P Peter Wolynec
- Bio21 Molecular Science and Biotechnology Institute, University of MelbourneMelbourne, Australia
| | - Vladimir A Likić
- Bio21 Molecular Science and Biotechnology Institute, University of MelbourneMelbourne, Australia
| | - Anthony W Purcell
- Department of Biochemistry and Molecular Biology, University of MelbourneMelbourne, Australia
- Bio21 Molecular Science and Biotechnology Institute, University of MelbourneMelbourne, Australia
| | - Susan K Buchanan
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesda, MD, USA
| | - Trevor Lithgow
- Department of Biochemistry and Molecular Biology, University of MelbourneMelbourne, Australia
- Bio21 Molecular Science and Biotechnology Institute, University of MelbourneMelbourne, Australia
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5
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Marani P, Wagner S, Baars L, Genevaux P, de Gier JW, Nilsson I, Casadio R, von Heijne G. New Escherichia coli outer membrane proteins identified through prediction and experimental verification. Protein Sci 2006; 15:884-9. [PMID: 16522795 PMCID: PMC2242486 DOI: 10.1110/ps.051889506] [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: 10/24/2022]
Abstract
Many new Escherichia coli outer membrane proteins have recently been identified by proteomics techniques. However, poorly expressed proteins and proteins expressed only under certain conditions may escape detection when wild-type cells are grown under standard conditions. Here, we have taken a complementary approach where candidate outer membrane proteins have been identified by bioinformatics prediction, cloned and overexpressed, and finally localized by cell fractionation experiments. Out of eight predicted outer membrane proteins, we have confirmed the outer membrane localization for five-YftM, YaiO, YfaZ, CsgF, and YliI--and also provide preliminary data indicating that a sixth--YfaL--may be an outer membrane autotransporter.
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Affiliation(s)
- Paola Marani
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
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6
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Mao F, Su Z, Olman V, Dam P, Liu Z, Xu Y. Mapping of orthologous genes in the context of biological pathways: An application of integer programming. Proc Natl Acad Sci U S A 2005; 103:129-34. [PMID: 16373500 PMCID: PMC1325003 DOI: 10.1073/pnas.0509737102] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mapping biological pathways across microbial genomes is a highly important technique in functional studies of biological systems. Existing methods mainly rely on sequence-based orthologous gene mapping, which often leads to suboptimal mapping results because sequence-similarity information alone does not contain sufficient information for accurate identification of orthology relationship. Here we present an algorithm for pathway mapping across microbial genomes. The algorithm takes into account both sequence similarity and genomic structure information such as operons and regulons. One basic premise of our approach is that a microbial pathway could generally be decomposed into a few operons or regulons. We formulated the pathway-mapping problem to map genes across genomes to maximize their sequence similarity under the constraint that the mapped genes be grouped into a few operons, preferably coregulated in the target genome. We have developed an integer-programming algorithm for solving this constrained optimization problem and implemented the algorithm as a computer software program, p-map. We have tested p-map on a number of known homologous pathways. We conclude that using genomic structure information as constraints could greatly improve the pathway-mapping accuracy over methods that use sequence-similarity information alone.
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Affiliation(s)
- Fenglou Mao
- Computational Systems Biology Laboratory, Biochemistry and Molecular Biology Department, University of Georgia, A110 Life Science Building, 120 Green Street, Athens, GA 30602, USA
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7
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Zhou J, Xu Z. The structural view of bacterial translocation-specific chaperone SecB: implications for function. Mol Microbiol 2005; 58:349-57. [PMID: 16194224 DOI: 10.1111/j.1365-2958.2005.04842.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
SecB is a molecular chaperone that functions in bacterial post-translational protein translocation pathway. It maintains newly synthesized precursor polypeptide chains in a translocation-competent state and guides them to the translocon via its high-affinity binding to the ligand as well as to the membrane-embedded ATPase SecA. Recent advances in elucidating the structures of SecB have enabled the examination of protein function in the structural context. Structures of SecB from both Haemophilus influenzae and Escherichia coli support the early two-subsite polypeptide-binding model. In addition, the detailed molecular interaction between SecB and SecA was revealed by a structure of SecB in complex with the C-terminal zinc-containing domain of SecA. These observations explain the dual role of SecB plays in the translocation pathway, as a molecular chaperone and a specific targeting factor. A model of SecB-SecA complex suggests that the binding of SecA to SecB changes the conformation of the polypeptide binding sites in the chaperone, enabling transfer of precursor polypeptides from SecB to SecA. Recent studies also show the presence of a second zinc-independent SecB binding site in SecA and the new interaction might contribute to the function of SecB.
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Affiliation(s)
- Jiahai Zhou
- Department of Biological Chemistry, Medical School and Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109-2216, USA
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8
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Mallik I, Smith MA, Flower AM. Recognition of secretory proteins in Escherichia coli requires signals in addition to the signal sequence and slow folding. BMC Microbiol 2002; 2:32. [PMID: 12427258 PMCID: PMC137694 DOI: 10.1186/1471-2180-2-32] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2002] [Accepted: 11/11/2002] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND The Sec-dependent protein export apparatus of Escherichia coli is very efficient at correctly identifying proteins to be exported from the cytoplasm. Even bacterial strains that carry prl mutations, which allow export of signal sequence-defective precursors, accurately differentiate between cytoplasmic and mutant secretory proteins. It was proposed previously that the basis for this precise discrimination is the slow folding rate of secretory proteins, resulting in binding by the secretory chaperone, SecB, and subsequent targeting to translocase. Based on this proposal, we hypothesized that a cytoplasmic protein containing a mutation that slows its rate of folding would be recognized by SecB and therefore targeted to the Sec pathway. In a Prl suppressor strain the mutant protein would be exported to the periplasm due to loss of ability to reject non-secretory proteins from the pathway. RESULTS In the current work, we tested this hypothesis using a mutant form of lambda repressor that folds slowly. No export of the mutant protein was observed, even in a prl strain. We then examined binding of the mutant lambda repressor to SecB. We did not observe interaction by either of two assays, indicating that slow folding is not sufficient for SecB binding and targeting to translocase. CONCLUSIONS These results strongly suggest that to be targeted to the export pathway, secretory proteins contain signals in addition to the canonical signal sequence and the rate of folding.
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Affiliation(s)
- Ipsita Mallik
- Department of Microbiology and Immunology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202-9037
| | - Margaret A Smith
- Department of Microbiology and Immunology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202-9037
| | - Ann M Flower
- Department of Microbiology and Immunology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202-9037
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Adams H, Scotti PA, De Cock H, Luirink J, Tommassen J. The presence of a helix breaker in the hydrophobic core of signal sequences of secretory proteins prevents recognition by the signal-recognition particle in Escherichia coli. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:5564-71. [PMID: 12423355 DOI: 10.1046/j.1432-1033.2002.03262.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Signal sequences often contain alpha-helix-destabilizing amino acids within the hydrophobic core. In the precursor of the Escherichia coli outer-membrane protein PhoE, the glycine residue at position -10 (Gly-10) is thought to be responsible for the break in the alpha-helix. Previously, we showed that substitution of Gly-10 by alpha-helix-promoting residues (Ala, Cys or Leu) reduced the proton-motive force dependency of the translocation of the precursor, but the actual role of the helix breaker remained obscure. Here, we considered the possibility that extension of the alpha-helical structure in the signal sequence resulting from the Gly-10 substitutions affects the targeting pathway of the precursor. Indeed, the mutations resulted in reduced dependency on SecB for targeting in vivo. In vitro cross-linking experiments revealed that the G-10L and G-10C mutant PhoE precursors had a dramatically increased affinity for P48, one of the constituents of the signal-recognition particle (SRP). Furthermore, in vitro cross-linking experiments revealed that the G-10L mutant protein is routed to the SecYEG translocon via the SRP pathway, the targeting pathway that is exploited by integral inner-membrane proteins. Together, these data indicate that the helix breaker in cleavable signal sequences prevents recognition by SRP and is thereby, together with the hydrophobicity of the signal sequence, a determinant of the targeting pathway.
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Affiliation(s)
- Hendrik Adams
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, The Netherlands
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10
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Adams H, Scotti PA, Luirink J, Tommassen J. Defective translocation of a signal sequence mutant in a prlA4 suppressor strain of Escherichia coli. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:5572-80. [PMID: 12423356 DOI: 10.1046/j.1432-1033.2002.03263.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the accompanying paper [Adams, H., Scotti, P.A., de Cock, H., Luirink, J. & Tommassen, J. (2002) Eur. J. Biochem.269, 5564-5571], we showed that the precursor of outer-membrane protein PhoE of Escherichia coli with a Gly to Leu substitution at position -10 in the signal sequence (G-10L) is targeted to the SecYEG translocon via the signal-recognition particle (SRP) route, instead of via the SecB pathway. Here, we studied the fate of the mutant precursor in a prlA4 mutant strain. prlA mutations, located in the secY gene, have been isolated as suppressors that restore the export of precursors with defective signal sequences. Remarkably, the G-10L mutant precursor, which is normally exported in a wild-type strain, accumulated strongly in a prlA4 mutant strain. In vitro cross-linking experiments revealed that the precursor is correctly targeted to the prlA4 mutant translocon. However, translocation across the cytoplasmic membrane was defective, as appeared from proteinase K-accessibility experiments in pulse-labeled cells. Furthermore, the mutant precursor was found to accumulate when expressed in a secY40 mutant, which is defective in the insertion of integral-membrane proteins but not in protein translocation. Together, these data suggest that SecB and SRP substrates are differently processed at the SecYEG translocon.
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Affiliation(s)
- Hendrik Adams
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, The Netherlands
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11
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Harms N, Koningstein G, Dontje W, Muller M, Oudega B, Luirink J, de Cock H. The early interaction of the outer membrane protein phoe with the periplasmic chaperone Skp occurs at the cytoplasmic membrane. J Biol Chem 2001; 276:18804-11. [PMID: 11278858 DOI: 10.1074/jbc.m011194200] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Spheroplasts were used to study the early interactions of newly synthesized outer membrane protein PhoE with periplasmic proteins employing a protein cross-linking approach. Newly translocated PhoE protein could be cross-linked to the periplasmic chaperone Skp at the periplasmic side of the inner membrane. To study the timing of this interaction, a PhoE-dihydrofolate reductase hybrid protein was constructed that formed translocation intermediates, which had the PhoE moiety present in the periplasm and the dihydrofolate reductase moiety tightly folded in the cytoplasm. The hybrid protein was found to cross-link to Skp, indicating that PhoE closely interacts with the chaperone when the protein is still in a transmembrane orientation in the translocase. Removal of N-terminal parts of PhoE protein affected Skp binding in a cumulative manner, consistent with the presence of two Skp-binding sites in that region. In contrast, deletion of C-terminal parts resulted in variable interactions with Skp, suggesting that interaction of Skp with the N-terminal region is influenced by parts of the C terminus of PhoE protein. Both the soluble as well as the membrane-associated Skp protein were found to interact with PhoE. The latter form is proposed to be involved in the initial interaction with the N-terminal regions of the outer membrane protein.
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Affiliation(s)
- N Harms
- Department of Molecular Microbiology, Institute of Molecular Biological Sciences, Biocentrum Amsterdam, De Boelelaan 1087, Amsterdam 1081 HV, The Netherlands
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12
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Behrens S, Maier R, de Cock H, Schmid FX, Gross CA. The SurA periplasmic PPIase lacking its parvulin domains functions in vivo and has chaperone activity. EMBO J 2001; 20:285-94. [PMID: 11226178 PMCID: PMC140197 DOI: 10.1093/emboj/20.1.285] [Citation(s) in RCA: 183] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The Escherichia coli periplasmic peptidyl-prolyl isomerase (PPIase) SurA is involved in the maturation of outer membrane porins. SurA consists of a substantial N-terminal region, two iterative parvulin-like domains and a C-terminal tail. Here we show that a variant of SurA lacking both parvulin-like domains exhibits a PPIase-independent chaperone-like activity in vitro and almost completely complements the in vivo function of intact SurA. SurA interacts preferentially (>50-fold) with in vitro synthesized porins over other similarly sized proteins, leading us to suggest that the chaperone-like function of SurA preferentially facilitates maturation of outer membrane proteins.
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Affiliation(s)
- Susanne Behrens
- Departments of Stomatology and Microbiology, University of California, San Francisco, 513 Parnassus Avenue, CA 94143, USA, Abteilung Molekulare Genetik und Präparative Molekularbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstrasse 8, D-37077 Göttingen, Laboratorium für Biochemie, Universität Bayreuth, D-95440 Bayreuth, Germany and Department of Molecular Cell Biology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands Corresponding author e-mail:
| | - Raimund Maier
- Departments of Stomatology and Microbiology, University of California, San Francisco, 513 Parnassus Avenue, CA 94143, USA, Abteilung Molekulare Genetik und Präparative Molekularbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstrasse 8, D-37077 Göttingen, Laboratorium für Biochemie, Universität Bayreuth, D-95440 Bayreuth, Germany and Department of Molecular Cell Biology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands Corresponding author e-mail:
| | - Hans de Cock
- Departments of Stomatology and Microbiology, University of California, San Francisco, 513 Parnassus Avenue, CA 94143, USA, Abteilung Molekulare Genetik und Präparative Molekularbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstrasse 8, D-37077 Göttingen, Laboratorium für Biochemie, Universität Bayreuth, D-95440 Bayreuth, Germany and Department of Molecular Cell Biology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands Corresponding author e-mail:
| | - Franz X. Schmid
- Departments of Stomatology and Microbiology, University of California, San Francisco, 513 Parnassus Avenue, CA 94143, USA, Abteilung Molekulare Genetik und Präparative Molekularbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstrasse 8, D-37077 Göttingen, Laboratorium für Biochemie, Universität Bayreuth, D-95440 Bayreuth, Germany and Department of Molecular Cell Biology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands Corresponding author e-mail:
| | - Carol A. Gross
- Departments of Stomatology and Microbiology, University of California, San Francisco, 513 Parnassus Avenue, CA 94143, USA, Abteilung Molekulare Genetik und Präparative Molekularbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstrasse 8, D-37077 Göttingen, Laboratorium für Biochemie, Universität Bayreuth, D-95440 Bayreuth, Germany and Department of Molecular Cell Biology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands Corresponding author e-mail:
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13
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van Voorst F, Vereyken IJ, de Kruijff B. The high affinity ATP binding site modulates the SecA-precursor interaction. FEBS Lett 2000; 486:57-62. [PMID: 11108843 DOI: 10.1016/s0014-5793(00)02209-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
SecA is the central component of the protein-translocation machinery of Escherichia coli. It is able to interact with the precursor protein, the chaperone SecB, the integral membrane protein complex SecYEG, acidic phospholipids and its own mRNA. We studied the interaction between prePhoE and SecA by using a site-specific photocrosslinking strategy. We found that SecA is able to interact with both the signal sequence and the mature domain of prePhoE. Furthermore, this interaction was dependent on the type of nucleotide bound. SecA in the ADP-bound conformation was unable to crosslink with the precursor, whereas the ATP-bound conformation was active in precursor crosslinking. The SecA-precursor interaction was maintained in the presence of E. coli phospholipids but was loosened by the presence of phosphatidylglycerol bilayers. Examining SecA ATP binding site mutants demonstrated that ATP hydrolysis at the N-terminal high affinity binding site is responsible for the changed interaction with the preprotein.
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Affiliation(s)
- F van Voorst
- CBLE, Institute of Biomembranes, Department of Biochemistry of Membranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
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14
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Abstract
SecA is an obligatory component of the complex hetero-septameric translocase of prokaryotes. It is unique in that it exists as two forms within the holoenzyme; first, as a structural component of the preprotein channel and second, as an ATP-dependent membrane cycling factor facilitating the translocation of a broad class of proteins across the cytoplasmic membrane. While the translocase activity of SecA appears to be functionally conserved, it is not clear whether the mechanisms of regulation of the secA gene are similarly maintained. The recent characterization of an ATP-dependent RNA helicase activity of SecA offers a unique mechanism for SecA to communicate the secretion status of the cell to the appropriate regulatory circuits simply by the unwinding of an appropriate RNA target. Resolution of these two activities through combined biochemical, genetic, and biophysical studies should lead to a better understanding of the role of SecA in bacterial secretion.
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Affiliation(s)
- M G Schmidt
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC 29425-2230, USA
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15
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De Cock H, Schäfer U, Potgeter M, Demel R, Müller M, Tommassen J. Affinity of the periplasmic chaperone Skp of Escherichia coli for phospholipids, lipopolysaccharides and non-native outer membrane proteins. Role of Skp in the biogenesis of outer membrane protein. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 259:96-103. [PMID: 9914480 DOI: 10.1046/j.1432-1327.1999.00010.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Skp protein of Escherichia coli has been proposed to be a periplasmic molecular chaperone involved in the biogenesis of outer membrane proteins. In this study, evidence is obtained that Skp exists in two different states characterized by their different sensitivity to proteases. The conversion between these states can be modulated in vitro by phospholipids, lipopolysaccharides and bivalent cations. Skp is able to associate with and insert into phospholipid membranes in vitro, indicating that it may associate with phospholipids in the inner and/or outer membrane in vivo. In addition, it interacts specifically with outer membrane proteins that are in their non-native state. We propose that Skp is required in vivo for the efficient targeting of unfolded outer membrane proteins to the membrane.
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Affiliation(s)
- H De Cock
- Department of Molecular Cell Biology, Utrecht University, The Netherlands
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16
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Fekkes P, de Wit JG, van der Wolk JP, Kimsey HH, Kumamoto CA, Driessen AJ. Preprotein transfer to the Escherichia coli translocase requires the co-operative binding of SecB and the signal sequence to SecA. Mol Microbiol 1998; 29:1179-90. [PMID: 9767586 DOI: 10.1046/j.1365-2958.1998.00997.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In Escherichia coli, precursor proteins are targeted to the membrane-bound translocase by the cytosolic chaperone SecB. SecB binds to the extreme carboxy-terminus of the SecA ATPase translocase subunit, and this interaction is promoted by preproteins. The mutant SecB proteins, L75Q and E77K, which interfere with preprotein translocation in vivo, are unable to stimulate in vitro translocation. Both mutants bind proOmpA but fail to support the SecA-dependent membrane binding of proOmpA because of a marked reduction in their binding affinities for SecA. The stimulatory effect of preproteins on the interaction between SecB and SecA exclusively involves the signal sequence domain of the preprotein, as it can be mimicked by a synthetic signal peptide and is not observed with a mutant preprotein (delta8proOmpA) bearing a non-functional signal sequence. Delta8proOmpA is not translocated across wild-type membranes, but the translocation defect is suppressed in inner membrane vesicles derived from a prIA4 strain. SecB reduces the translocation of delta8proOmpA into these vesicles and almost completely prevents translocation when, in addition, the SecB binding site on SecA is removed. These data demonstrate that efficient targeting of preproteins by SecB requires both a functional signal sequence and a SecB binding domain on SecA. It is concluded that the SecB-SecA interaction is needed to dissociate the mature preprotein domain from SecB and that binding of the signal sequence domain to SecA is required to ensure efficient transfer of the preprotein to the translocase.
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Affiliation(s)
- P Fekkes
- Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands
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17
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Randall LL, Topping TB, Suciu D, Hardy SJ. Calorimetric analyses of the interaction between SecB and its ligands. Protein Sci 1998; 7:1195-200. [PMID: 9605324 PMCID: PMC2144013 DOI: 10.1002/pro.5560070514] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
SecB is a chaperone in Escherichia coli dedicated to export of proteins from the cytoplasm to the periplasm and outer membrane. It functions to bind and deliver precursors of exported proteins to the translocation apparatus before they fold into their native structures, thus maintaining them in a competent state for translocation across the membrane. The natural ligands of SecB are precursor proteins containing leader sequences. There are numerous reports in the literature indicating that SecB does not specifically recognize the leader peptides. However, two published investigations have concluded that the leader peptide is the recognition element (Watanabe M, Blobel G. 1989. Cell 58:685-705; Watanabe M, Blobel G. 1995. Proc Natl Acad Sci USA 92:10133-10136). In this work we use titration calorimetry to show that SecB binds two physiological ligands, which contain leader sequences, with no higher affinity than the same molecules lacking their leader sequences. Indeed, for one ligand the presence of the leader sequence reduces the affinity. Therefore, it can be concluded that the leader sequence provides no positive contribution to the binding energy.
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Affiliation(s)
- L L Randall
- Department of Biochemistry and Biophysics, Washington State University, Pullman 99164-4660, USA
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18
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Randall LL, Topping TB, Smith VF, Diamond DL, Hardy SJ. SecB: a chaperone from Escherichia coli. Methods Enzymol 1998; 290:444-59. [PMID: 9534181 DOI: 10.1016/s0076-6879(98)90037-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- L L Randall
- Department of Biochemistry, Washington State University, Pullman 99164-4660, USA
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19
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20
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de Cock H, Randall LL. Correlation between requirement for SecA during export and folding properties of precursor polypeptides. Mol Microbiol 1998; 27:469-76. [PMID: 9484900 DOI: 10.1046/j.1365-2958.1998.00695.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The structural complexity of a ligand in association with the molecular chaperones SecB and SecA was investigated using three species of precursor maltose-binding protein, which differ in their stability as a result of an amino acid substitution in each that affects the rate of folding of the polypeptide. In the presence of high concentrations of both SecB and SecA, the precursors were translocated in vitro with indistinguishable kinetics. However, when SecA was limiting, the translocation was more rapid for precursor species, which had lower stability in the native state relative to the stability of the wild-type precursor. We propose that, when in complex with SecB, precursors can form an element of tertiary structure and that these tertiary contacts are blocked when SecA is bound.
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Affiliation(s)
- H de Cock
- Department of Biochemistry and Biophysics, Washington State University, Pullman, USA.
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21
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Randall LL, Topping TB, Hardy SJ, Pavlov MY, Freistroffer DV, Ehrenberg M. Binding of SecB to ribosome-bound polypeptides has the same characteristics as binding to full-length, denatured proteins. Proc Natl Acad Sci U S A 1997; 94:802-7. [PMID: 9023337 PMCID: PMC19594 DOI: 10.1073/pnas.94.3.802] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The interaction of the chaperone SecB with ribosome-bound polypeptides that are in the process of elongation has been studied using an in vitro protein synthesis system. The binding is characterized by the same properties as those demonstrated for the binding of SecB to full-length proteins that are in nonnative conformation: it is readily reversible and has no specificity for the leader peptide. In addition, it is shown that the growing polypeptide chains must achieve a critical length to bind tightly enough to allow their isolation in complex with SecB. This explains the longstanding observation that, even when export is cotranslational, it begins late in synthesis. Furthermore, the required length is approximately the same as the length that defines the binding frame within denatured, full-length proteins bound to SecB.
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Affiliation(s)
- L L Randall
- Department of Biochemistry and Biophysics, Washington State University, Pullman 99164-4660, USA
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22
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Van Raalte AL, Demel RA, Verberkmoes G, Breukink E, Keller RC, De Kruijff B. Influence of the signal sequence and chaperone SecB on the interaction between precursor protein prePhoE and phospholipids. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 235:207-14. [PMID: 8631331 DOI: 10.1111/j.1432-1033.1996.00207.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
To investigate in a direct way the interaction between a precursor protein and phospholipids, monolayer studies were performed using the purified precursor of Escherichia coli outer-membrane protein PhoE. It was demonstrated that prePhoE can insert efficiently into monolayers of dioleoylglycerophosphoglycerol (Ole2GroPGro) and dioleoylglycerophosphoethanolamine (Ole2GroPEtn), this insertion was mainly driven by hydrophobic forces. Compared with previous results obtained with PhoE signal peptide, the full-length precursor protein does not show the specific interaction with acidic lipids. PrePhoE inserted into a Ole2GroPGro monolayer occupies an area of 28 +/- 3 [corrected] nm2/molecule, which is approximately 10-fold larger than the area occupied by the PhoE signal peptide. The purified mature PhoE protein has a lower capacity to insert into Ole2GroPGro and Ole2GroPEtn monolayers and is, in contrast to prePhoE, fully accessible to proteinase K after interacting with a Ole2GroPGro monolayer. The results demonstrate that in the context of the precursor protein both the signal sequence and mature domain of prePhoE insert into lipid monolayers. It was found that PhoE, like prePhoE, can form in vitro a complex with the cytosolic chaperone SecB. Complexation with SecB increases the insertion of (pre)PhoE into acidic lipid monolayers. The high lipid affinity of prePhoE was also demonstrated by vesicle-binding experiments which showed that SecB dissociates from the SecB-prePhoE complex upon binding of the precursor to the bilayer. The implications of these findings for preprotein translocation are discussed and in addition some extrapolations to the insertion of PhoE into the outer membrane are made.
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Affiliation(s)
- A L Van Raalte
- Department of Biochemistry of Membranes, Utrecht University, The Netherlands
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23
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Rusch SL, Kendall DA. Protein transport via amino-terminal targeting sequences: common themes in diverse systems. Mol Membr Biol 1995; 12:295-307. [PMID: 8747274 DOI: 10.3109/09687689509072431] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Many proteins that are synthesized in the cytoplasm of cells are ultimately found in non-cytoplasmic locations. The correct targeting and transport of proteins must occur across bacterial cell membranes, the endoplasmic reticulum membrane, and those of mitochondria and chloroplasts. One unifying feature among transported proteins in these systems is the requirement for an amino-terminal targeting signal. Although the primary sequence of targeting signals varies substantially, many patterns involving overall properties are shared. A recent surge in the identification of components of the transport apparatus from many different systems has revealed that these are also closely related. In this review we describe some of the key components of different transport systems and highlight these common features.
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Affiliation(s)
- S L Rusch
- Department of Molecular and Cell Biology, University of Connecticut, Storrs 06269, USA
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24
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Fekkes P, den Blaauwen T, Driessen AJ. Diffusion-limited interaction between unfolded polypeptides and the Escherichia coli chaperone SecB. Biochemistry 1995; 34:10078-85. [PMID: 7543278 DOI: 10.1021/bi00031a032] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
SecB is a chaperone dedicated to protein translocation in Escherichia coli. SecB binds to a subset of precursor proteins, and targets them in a translocation-competent state to the SecA subunit of the translocase. The nature and kinetics of the interaction of SecB with polypeptides were studied by spectroscopic techniques using the reduced form of bovine pancreatic trypsin inhibitor (BPTI) as a model substrate. Binding of SecB to BPTI resulted in an increase in the fluorescence of the surface-exposed tryptophan residue 36 of SecB. SecB reversibly binds BPTI in stoichiometric amounts. Labeling of BPTI with the fluorophore acrylodan allowed the analysis of the binding reaction at nanomolar concentrations. High-affinity binding (KD of 5.4 nM) of labeled BPTI to SecB resulted in a blue shift of the acrylodan emission maximum and an increase in the fluorescence quantum yield, suggesting that BPTI binds in an apolar environment. Stopped-flow acquisition of rate constants of complex formation between SecB and BPTI yielded a second-order binding rate constant of 5 x 10(9) M-1 s-1, and a dissociation rate constant of 48 s-1. These data demonstrate that in vitro, the association of SecB with polypeptide substrates is limited by the rate of collision. In vivo, SecB binding is selective, and predominantly occurs with nascent polypeptides. Since these chains are not expected to fold into stable structures, SecB association may be governed by "more or less" specific interactions and be limited by the rate of chain elongation rather than the rate of folding.
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Affiliation(s)
- P Fekkes
- Department of Microbiology, University of Groningen, Haren, The Netherlands
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25
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Khisty VJ, Randall LL. Demonstration in vivo that interaction of maltose-binding protein with SecB is determined by a kinetic partitioning. J Bacteriol 1995; 177:3277-82. [PMID: 7768828 PMCID: PMC177021 DOI: 10.1128/jb.177.11.3277-3282.1995] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
An early step in the export of maltose-binding protein to the periplasm is interaction with the molecular chaperone SecB. We demonstrate that binding to SecB in vivo is determined by a kinetic partitioning between the folding of maltose-binding protein to its native state and its association with SecB. A complex of SecB and a species of maltose-binding protein that folds slowly is shown to be longer-lived than a complex of the wild-type maltose-binding protein and SecB. In addition, we show that incomplete nascent chains, which are unable to fold, remain complexed with SecB.
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Affiliation(s)
- V J Khisty
- Department of Biochemistry and Biophysics, Washington State University, Pullman 99164-4660, USA
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26
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Powers EL, Randall LL. Export of periplasmic galactose-binding protein in Escherichia coli depends on the chaperone SecB. J Bacteriol 1995; 177:1906-7. [PMID: 7896722 PMCID: PMC176827 DOI: 10.1128/jb.177.7.1906-1907.1995] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The efficient export of galactose-binding protein to the periplasm of Escherichia coli is shown to be dependent on the presence of the cytosolic chaperone SecB.
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Affiliation(s)
- E L Powers
- Department of Genetics and Cell Biology, Washington State University, Pullman 99164-4660
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27
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Export and assembly of outer membrane proteins in E. coli. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s1874-5172(06)80011-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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28
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Arkowitz RA, Bassilana M. Protein translocation in Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1197:311-43. [PMID: 7819269 DOI: 10.1016/0304-4157(94)90012-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- R A Arkowitz
- MRC Laboratory of Molecular Biology, Cambridge, UK
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29
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30
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Flower AM, Doebele RC, Silhavy TJ. PrlA and PrlG suppressors reduce the requirement for signal sequence recognition. J Bacteriol 1994; 176:5607-14. [PMID: 8083155 PMCID: PMC196762 DOI: 10.1128/jb.176.18.5607-5614.1994] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Selection for suppressors of defects in the signal sequence of secretory proteins has led most commonly to identification of prlA alleles and less often to identification of prlG alleles. These genes, secY/prlA and secE/prlG, encode integral membrane components of the protein translocation system of Escherichia coli. We demonstrate that an outer membrane protein, LamB, that lacks a signal sequence can be exported with reasonable efficiency in both prlA and prlG suppressor strains. Although the signal sequence is not absolutely required for export of LamB, the level of export in the absence of prl suppressor alleles is exceedingly low. Such strains are phenotypically LamB-, and functional LamB can be detected only by using sensitive infectious-center assays. Suppression of the LamB signal sequence deletion is dependent on normal components of the export pathway, indicating that suppression is not occurring through a bypass mechanism. Our results indicate that the majority of the known prlA suppressors function by an identical mechanism and, further, that the prlG suppressors work in a similar fashion. We propose that both PrlA and PrlG suppressors lack a proofreading activity that normally rejects defective precursors from the export pathway.
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Affiliation(s)
- A M Flower
- Department of Molecular Biology, Princeton University, New Jersey 08544
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31
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Nouwen N, Tommassen J, de Kruijff B. Requirement for conformational flexibility in the signal sequence of precursor protein. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)33968-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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32
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Topping TB, Randall LL. Determination of the binding frame within a physiological ligand for the chaperone SecB. Protein Sci 1994; 3:730-6. [PMID: 8061603 PMCID: PMC2142715 DOI: 10.1002/pro.5560030502] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The hallmark of the class of proteins called chaperones is the amazing ability to bind tightly to a wide array of polypeptide ligands that have no consensus in sequence; chaperones recognize non-native structure. As a step in the elucidation of the molecular mechanism of such remarkable binding, we have characterized complexes between the bacterial chaperone SecB and a series of ligands related to maltose-binding protein. SecB interacts at multiple sites on its polypeptide ligand. The entire binding region covers approximately half of the primary sequence of maltose-binding protein and comprises contiguous sites positioned around the center of the sequence.
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Affiliation(s)
- T B Topping
- Department of Biochemistry and Biophysics, Washington State University, Pullman 99164-4660
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33
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Affiliation(s)
- M Müller
- Institut für Physikalische Biochemie, Universität München, Germany
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34
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Strobel SM, Cannon JG, Bassford PJ. Regions of maltose-binding protein that influence SecB-dependent and SecA-dependent export in Escherichia coli. J Bacteriol 1993; 175:6988-95. [PMID: 8226642 PMCID: PMC206826 DOI: 10.1128/jb.175.21.6988-6995.1993] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
In Escherichia coli, the efficient export of maltose-binding protein (MBP) is dependent on the chaperone SecB, whereas export of ribose-binding protein (RBP) is SecB independent. To localize the regions of MBP involved in interaction with SecB, hybrids between MBP and RBP in SecB mutant cells were constructed and analyzed. One hybrid consisted of the signal peptide and first third of the mature moiety of MBP, followed by the C-terminal two-thirds of RBP (MBP-RBP112). This hybrid was dependent upon SecB for its efficient export and exhibited a strong export defect in secA mutant cells. A hybrid between RBP and MBP with the same fusion point was also constructed (RBP-MBP116). The RBP-MBP116 hybrid remained SecB independent and only exhibited a partial export defect in secA mutant cells. In addition, MBP species with specific alterations in the early mature region were less dependent on SecB for their efficient export. The export of these altered MBP species was also less affected in secA mutant cells and in cells treated with sodium azide. These results present additional evidence for the targeting role of SecB.
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Affiliation(s)
- S M Strobel
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill 27599-7290
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35
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Jacq A, Holland B. The components of the Escherichia coli protein-transport apparatus. Curr Opin Struct Biol 1993. [DOI: 10.1016/0959-440x(93)90080-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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36
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Oudega B, Mol O, van Ulsen P, Stegehuis F, van der Wal FJ, Luirink J. Escherichia coli SecB, SecA, and SecY proteins are required for expression and membrane insertion of the bacteriocin release protein, a small lipoprotein. J Bacteriol 1993; 175:1543-7. [PMID: 8444816 PMCID: PMC193245 DOI: 10.1128/jb.175.5.1543-1547.1993] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The SecB, SecA, and SecY dependency of a small outer membrane lipoprotein in Escherichia coli, the bacteriocin release protein (BRP), was studied. The detrimental effect of BRP expression on the culture turbidity (quasi-lysis) was strongly reduced in the sec mutants. Immunoblotting and radioactive labeling experiments showed that the expression, membrane insertion, and processing of the BRP precursor are dependent on SecB, SecA, and SecY. Labeling experiments with hybrid BRP gene constructs revealed that the mature part of the BRP precursor and not its stable signal sequence is important for its SecB dependency.
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Affiliation(s)
- B Oudega
- Department of Molecular Microbiology, Faculty of Biology, Vrije Universiteit, Amsterdam, The Netherlands
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37
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Kleerebezem M, Tommassen J. Expression of the pspA gene stimulates efficient protein export in Escherichia coli. Mol Microbiol 1993; 7:947-56. [PMID: 8387148 DOI: 10.1111/j.1365-2958.1993.tb01186.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Expression of several mutant forms of outer membrane protein PhoE of Escherichia coli, which are disturbed in normal biogenesis, resulted in high expression of a 26 kDa protein. This 26 kDa protein fractionated as a peripherally bound inner membrane protein. It appeared to be identical to a previously identified protein (PspA = phage shock protein A) of unknown function that is induced upon infection of E. coli with filamentous phages. PspA was not expressed upon synthesis of mutant PhoE proteins in a secB mutant, nor upon expression of a PhoE mutant that lacks the signal sequence, suggesting that entrance into the export pathway of prePhoE is essential for induction. PspA synthesis was also induced under other conditions that are known to block the export apparatus, i.e. in secA, secD and secF mutants when grown at their non-permissive temperature or upon induction of the synthesis of MalE-LacZ or LamB-LacZ hybrid proteins. The inducing conditions for PspA synthesis suggested a role for this protein in export. In vivo pulse-chase experiments showed that the translocation of (mutant) prePhoE and of the precursors of other exported proteins was retarded in a pspA mutant strain. Also, in in vitro translocation assays, a role for PspA in protein transport could be demonstrated.
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Affiliation(s)
- M Kleerebezem
- Department of Molecular Cell Biology, University of Utrecht, The Netherlands
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38
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Collier DN. SecB: a molecular chaperone of Escherichia coli protein secretion pathway. ADVANCES IN PROTEIN CHEMISTRY 1993; 44:151-93. [PMID: 8100379 DOI: 10.1016/s0065-3233(08)60567-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- D N Collier
- CR&D, E. I. du Pont de Nemours & Co., Wilmington, Delaware 19880
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