Mechanistic link between ? 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 ? barrel ("?") domain that anchors the protein to the outer membrane. The ? 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 ? 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 ? domain and delay the initiation of passenger domain translocation. Site-specific photocrosslinking experiments revealed that the mutations slow the insertion of the ? domain into the outer membrane, but do not delay the binding of the ? domain to the factor that mediates the insertion reaction (the Bam complex). Our results demonstrate that the ? 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 ? barrel proteins in a multistep process that can be perturbed by minor structural defects in client proteins.

SUBMITTER: Pavlova O 

PROVIDER: S-EPMC3593871 | biostudies-other | 2013 Mar

REPOSITORIES: biostudies-other