title: Multiple driving forces required for efficient secretion of autotransporter virulence proteins.
abstract: Autotransporter (AT) proteins are a broad class of virulence proteins from Gram-negative bacterial pathogens that require their own C-terminal transmembrane domain to translocate their N-terminal passenger across the bacterial outer membrane (OM). But given the unavailability of ATP or a proton gradient across the OM, it is unknown what energy source(s) drives this process. Here we used a combination of computational and experimental approaches to quantitatively compare proposed AT OM translocation mechanisms. We show directly for the first time that when translocation was blocked an AT passenger remained unfolded in the periplasm. We demonstrate that AT secretion is a kinetically controlled, non-equilibrium process coupled to folding of the passenger and propose a model connecting passenger conformation to secretion kinetics. These results reconcile seemingly contradictory reports regarding the importance of passenger folding as a driving force for OM translocation but also reveal that another energy source is required to initiate translocation.
authors: From the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556.
authors: Igor
authors: I
authors: Drobnak
authors: From the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556.
authors: Esther
authors: E
authors: Braselmann
authors: From the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 pclark1@nd.edu.
authors: Patricia L
authors: PL
authors: Clark
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001886:Bordetella pertussis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D007700:Kinetics; D056004:Molecular Dynamics Simulation; D009154:Mutation; D019897:Periplasm / Q000737:chemistry / Q000378:metabolism; D010957:Plasmids / Q000737:chemistry* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013816:Thermodynamics; D014774:Virulence; D010566:Virulence Factors, Bordetella / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001618:beta-Lactamases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D011994:Recombinant Proteins; D010566:Virulence Factors, Bordetella; C068929:pertactin; D001618:beta-Lactamases
keywords: Autotransporter; Bioenergetics; Kinetics; Outer Membrane; Periplasm; Protein Folding; Protein Secretion; Thermodynamics; Translocation; Virulence Factor