期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：45
页码：19120-19125
DOI：10.1073/pnas.0907912106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Autotransporters are a superfamily of virulence factors produced by Gram-negative bacteria consisting of a large N-terminal extracellular domain ("passenger domain") and a C-terminal {beta} barrel domain ("{beta} domain"). The mechanism by which the passenger domain is translocated across the outer membrane (OM) is unknown. Here we show that the insertion of a small linker into the passenger domain of the Escherichia coli O157:H7 autotransporter EspP effectively creates a translocation intermediate by transiently stalling translocation near the site of the insertion. Using a site-specific photocrosslinking approach, we found that residues adjacent to the stall point interact with BamA, a component of a heterooligomeric complex (Bam complex) that catalyzes OM protein assembly, and that residues closer to the EspP N terminus interact with the periplasmic chaperones SurA and Skp. The EspP-BamA interaction was short-lived and could be detected only when passenger domain translocation was stalled. These results support a model in which molecular chaperones prevent misfolding of the passenger domain before its secretion and the Bam complex catalyzes both the integration of the {beta} domain into the OM and the translocation of the passenger domain across the OM in a C- to N-terminal direction.
