title: EscI: a crucial component of the type III secretion system forms the inner rod structure in enteropathogenic Escherichia coli.
abstract: The T3SS (type III secretion system) is a multi-protein complex that plays a central role in the virulence of many gram-negative bacterial pathogens. This apparatus spans both bacterial membranes and transports virulence factors from the bacterial cytoplasm into eukaryotic host cells. The T3SS exports substrates in a hierarchical and temporal manner. The first secreted substrates are the rod/needle proteins which are incorporated into the T3SS apparatus and are required for the secretion of later substrates, the translocators and effectors. In the present study, we provide evidence that rOrf8/EscI, a poorly characterized locus of enterocyte effacement-encoded protein, functions as the inner rod protein of the T3SS of EPEC (enteropathogenic Escherichia coli). We demonstrate that EscI is essential for type III secretion and is also secreted as an early substrate of the T3SS. We found that EscI interacts with EscU, the integral membrane protein that is linked to substrate specificity switching, implicating EscI in the substrate-switching event. Furthermore, we showed that EscI self-associates and interacts with the outer membrane secretin EscC, further supporting its function as an inner rod protein. Overall, the results of the present study suggest that EscI is the YscI/PrgJ/MxiI homologue in the T3SS of attaching and effacing pathogens.
authors.affiliation: Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Neta
authors.initials: N
authors.lastname: Sal-Man
authors.forename: Wanyin
authors.initials: W
authors.lastname: Deng
authors.forename: B Brett
authors.initials: BB
authors.lastname: Finlay
mesh_terms: D054308:Enteropathogenic Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: C570860:EscI protein, E coli; C529539:EscU protein, E coli; D029968:Escherichia coli Proteins; D037521:Virulence Factors