title: Functional analysis of the enteropathogenic Escherichia coli type III secretion system chaperone CesT identifies domains that mediate substrate interactions.
abstract: 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) translocated intimin receptor (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 alpha-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.
authors.affiliation: Centre for Molecular Microbiology and Infection (CMMI), Department of Biological Sciences, Flowers Building, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK. r.delahay@ic.ac.uk
authors.forename: Robin M
authors.initials: RM
authors.lastname: Delahay
authors.forename: Robert K
authors.initials: RK
authors.lastname: Shaw
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Elliott
authors.forename: James B
authors.initials: JB
authors.lastname: Kaper
authors.forename: Stuart
authors.initials: S
authors.lastname: Knutton
authors.forename: Gad
authors.initials: G
authors.lastname: Frankel
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D005816:Genetic Complementation Test; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C122044:CesT protein, E coli; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D011956:Receptors, Cell Surface; C109287:Tir protein, E coli