title: Mechanistic link between β barrel assembly and the initiation of autotransporter secretion.
abstract: Autotransporters are bacterial virulence factors that contain an N-terminal extracellular ("passenger") domain and a C-terminal β barrel ("β") domain that anchors the protein to the outer membrane. The β domain is required for passenger domain secretion, but its exact role in autotransporter biogenesis is unclear. Here we describe insights into the function of the β domain that emerged from an analysis of mutations in the Escherichia coli O157:H7 autotransporter EspP. We found that the G1066A and G1081D mutations slightly distort the structure of the β domain and delay the initiation of passenger domain translocation. Site-specific photocrosslinking experiments revealed that the mutations slow the insertion of the β domain into the outer membrane, but do not delay the binding of the β domain to the factor that mediates the insertion reaction (the Bam complex). Our results demonstrate that the β domain does not simply target the passenger domain to the outer membrane, but promotes translocation when it reaches a specific stage of assembly. Furthermore, our results provide evidence that the Bam complex catalyzes the membrane integration of β barrel proteins in a multistep process that can be perturbed by minor structural defects in client proteins.
authors: Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors: Olga
authors: O
authors: Pavlova
authors: Janine H
authors: JH
authors: Peterson
authors: Raffaele
authors: R
authors: Ieva
authors: Harris D
authors: HD
authors: Bernstein
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D019453:Escherichia coli O157 / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D005798:Genes, Bacterial; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry; D016297:Mutagenesis, Site-Directed; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D037521:Virulence Factors / Q000235:genetics / Q000502:physiology
chemical_list: D001425:Bacterial Outer Membrane Proteins; C503914:BamA protein, E coli; C513739:BamD protein, E coli; D029968:Escherichia coli Proteins; D046912:Multiprotein Complexes; D037521:Virulence Factors; C107189:EspP protein, E coli; D012697:Serine Endopeptidases