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Functional analysis of the enteropathogenic Escherichia coli type III secretion system chaperone CesT identifies domains that mediate substrate interactions
Author(s) -
Delahay Robin M.,
Shaw Robert K.,
Elliott Simon J.,
Kaper James B.,
Knutton Stuart,
Frankel Gad
Publication year - 2002
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2002.02740.x
Subject(s) - chaperone (clinical) , biology , secretion , intimin , type three secretion system , microbiology and biotechnology , effector , cytosol , virulence , escherichia coli , biochemistry , enterobacteriaceae , gene , medicine , pathology , enzyme
Summary In many Gram‐negative bacteria, a key indicator of pathogenic potential is the possession of a specialized type III secretion system, which is utilized to deliver virulence effector proteins directly into the host cell cytosol. Many of the proteins secreted from such systems require small cytosolic chaperones to maintain the secreted substrates in a secretion‐competent state. One such protein, CesT, serves a chaperone function for the enteropathogenic Escherichia coli (EPEC) t ranslocated i ntimin r eceptor (Tir) protein, which confers upon EPEC the ability to alter host cell morphology following intimate bacterial attachment. Using a combination of complementary biochemical approaches, functional domains of CesT that mediate intermolecular interactions, involved in both chaperone–chaperone and chaperone–substrate associations, were determined. The CesT N‐terminal is implicated in chaperone dimerization, whereas the amphipathic α ‐helical region of the C‐terminal, is intimately involved in substrate binding. By functional complementation of chaperone domains using the Salmonella SicA chaperone to generate chaperone chimeras, we show that CesT–Tir interaction proceeds by a mechanism potentially common to other type III secretion system chaperones.