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  • 1
    Publication Date: 2014-09-16
    Description: Curli are functional amyloid fibres that constitute the major protein component of the extracellular matrix in pellicle biofilms formed by Bacteroidetes and Proteobacteria (predominantly of the alpha and gamma classes). They provide a fitness advantage in pathogenic strains and induce a strong pro-inflammatory response during bacteraemia. Curli formation requires a dedicated protein secretion machinery comprising the outer membrane lipoprotein CsgG and two soluble accessory proteins, CsgE and CsgF. Here we report the X-ray structure of Escherichia coli CsgG in a non-lipidated, soluble form as well as in its native membrane-extracted conformation. CsgG forms an oligomeric transport complex composed of nine anticodon-binding-domain-like units that give rise to a 36-stranded beta-barrel that traverses the bilayer and is connected to a cage-like vestibule in the periplasm. The transmembrane and periplasmic domains are separated by a 0.9-nm channel constriction composed of three stacked concentric phenylalanine, asparagine and tyrosine rings that may guide the extended polypeptide substrate through the secretion pore. The specificity factor CsgE forms a nonameric adaptor that binds and closes off the periplasmic face of the secretion channel, creating a 24,000 A(3) pre-constriction chamber. Our structural, functional and electrophysiological analyses imply that CsgG is an ungated, non-selective protein secretion channel that is expected to employ a diffusion-based, entropy-driven transport mechanism.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4268158/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4268158/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Goyal, Parveen -- Krasteva, Petya V -- Van Gerven, Nani -- Gubellini, Francesca -- Van den Broeck, Imke -- Troupiotis-Tsailaki, Anastassia -- Jonckheere, Wim -- Pehau-Arnaudet, Gerard -- Pinkner, Jerome S -- Chapman, Matthew R -- Hultgren, Scott J -- Howorka, Stefan -- Fronzes, Remi -- Remaut, Han -- R01 A1073847/PHS HHS/ -- R01 AI048689/AI/NIAID NIH HHS/ -- R01 AI073847/AI/NIAID NIH HHS/ -- R01 AI099099/AI/NIAID NIH HHS/ -- R56 AI073847/AI/NIAID NIH HHS/ -- England -- Nature. 2014 Dec 11;516(7530):250-3. doi: 10.1038/nature13768. Epub 2014 Sep 14.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Structural and Molecular Microbiology, Structural Biology Research Center, VIB, Pleinlaan 2, 1050 Brussels, Belgium [2] Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium. ; 1] Unite G5 Biologie structurale de la secretion bacterienne, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France [2] UMR 3528, CNRS, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France. ; Structure et Fonction des Membranes Biologiques (SFMB), Universite Libre de Bruxelles, 1050 Brussels, Belgium. ; UMR 3528, CNRS, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France. ; Department of Molecular Microbiology and Microbial Pathogenesis, Washington University in Saint Louis School of Medicine, St Louis, Missouri 63110-1010, USA. ; Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109-1048, USA. ; Department of Chemistry, Institute for Structural and Molecular Biology, University College London, London WC1H 0AJ, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25219853" target="_blank"〉PubMed〈/a〉
    Keywords: Amyloid/*secretion ; Biofilms ; Cell Membrane ; Crystallography, X-Ray ; Diffusion ; Entropy ; Escherichia coli/*chemistry ; Escherichia coli Proteins/*chemistry/*metabolism ; Lipoproteins/*chemistry/*metabolism ; Membrane Transport Proteins/metabolism ; Models, Biological ; Models, Molecular ; Periplasm/metabolism ; Protein Conformation ; Protein Transport
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2014-03-29
    Description: Bacterial type IV secretion systems translocate virulence factors into eukaryotic cells, distribute genetic material between bacteria and have shown potential as a tool for the genetic modification of human cells. Given the complex choreography of the substrate through the secretion apparatus, the molecular mechanism of the type IV secretion system has proved difficult to dissect in the absence of structural data for the entire machinery. Here we use electron microscopy to reconstruct the type IV secretion system encoded by the Escherichia coli R388 conjugative plasmid. We show that eight proteins assemble in an intricate stoichiometric relationship to form an approximately 3 megadalton nanomachine that spans the entire cell envelope. The structure comprises an outer membrane-associated core complex connected by a central stalk to a substantial inner membrane complex that is dominated by a battery of 12 VirB4 ATPase subunits organized as side-by-side hexameric barrels. Our results show a secretion system with markedly different architecture, and consequently mechanism, to other known bacterial secretion systems.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3998870/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3998870/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Low, Harry H -- Gubellini, Francesca -- Rivera-Calzada, Angel -- Braun, Nathalie -- Connery, Sarah -- Dujeancourt, Annick -- Lu, Fang -- Redzej, Adam -- Fronzes, Remi -- Orlova, Elena V -- Waksman, Gabriel -- 079605/Wellcome Trust/United Kingdom -- 098302/Wellcome Trust/United Kingdom -- MR/K012401/1/Medical Research Council/United Kingdom -- England -- Nature. 2014 Apr 24;508(7497):550-3. doi: 10.1038/nature13081. Epub 2014 Mar 9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK [2] [3]. ; 1] Institut Pasteur, G5 Biologie structurale de la secretion bacterienne and UMR 3528-CNRS, 25 rue du Docteur Roux, 75015 Paris, France [2]. ; Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK. ; Institut Pasteur, G5 Biologie structurale de la secretion bacterienne and UMR 3528-CNRS, 25 rue du Docteur Roux, 75015 Paris, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24670658" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphatases/chemistry/genetics/metabolism/ultrastructure ; *Bacterial Secretion Systems/genetics ; Cell Membrane/metabolism ; Escherichia coli/*chemistry/cytology/genetics/*ultrastructure ; Escherichia coli Proteins/chemistry/isolation & ; purification/metabolism/ultrastructure ; Microscopy, Electron ; Models, Molecular ; Multiprotein Complexes/chemistry/genetics/metabolism/ultrastructure
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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