Identification of CesT, a chaperone for the type III secretion of Tir in enteropathogenicEscherichia coli

Abstract

SummaryThe locus of enterocyte effacement of enteropathogenic Escherichia coli encodes a type III secretion system, an outer membrane protein adhesin (intimin, the product of eae ) and Tir, a translocated protein that becomes a host cell receptor for intimin. Many type III secreted proteins require chaperones, which function to stabilize proteins, prevent inappropriate protein± protein interactions and aid in secretion. An open reading frame located between tir and eae, previously named orfU, was predicted to encode a protein with partial similarity to the Yersinia SycH chaperone. We examined the potential of the orfU gene product to serve as a chaperone for Tir. The orfU gene encoded a 15 kDa cytoplasmic protein that speci®cally interacted with Tir as demonstrated by the yeast two-hybrid assay, column binding and coimmunoprecipitation experiments. An orfU mutant was defective in attaching±effacing lesion formation and Tir secretion, but was unaffected in expression of other virulence factors. OrfU appeared to stabilize Tir levels in the cytoplasm, but was not absolutely necessary for secretion of Tir. Based upon the physical similarities, phenotypic characteristics and the demonstrated interaction with Tir, orfU is redesignated as cesT for the chaperone for E. coli secretion of T ir.

Investigation of EscA as a chaperone for the Edwardsiella tarda type III secretion system putative translocon component EseC

“…A limited number of NF-T3SS chaperones are reported to be membrane-associated, such as CesD and CesT from EPEC (Elliott et al, 1999;Wainwright & Kaper, 1998), YscB from Yersinia (Jackson et al, 1998), SseA from Salmonella (Zurawski & Stein, 2003) and EscC from Ed. tarda (Zheng et al, 2007).…”

Secretion of the housekeeping protein glyceraldehyde-3-phosphate dehydrogenase by the LEE-encoded type III secretion system in enteropathogenic Escherichia coli

“…The fact that the cognate chaperone is not absolutely required for protein secretion seems to be rather common for type III effectors in several pathogens (Parsot et al, 2003). Actually, there is evidence that Tir secretion is not strictly dependent on CesT as low levels of Tir can be detected in culture supernatants of cesT mutants (Elliot et al, 1999).…”

Hierarchical Delivery of an Essential Host Colonization Factor in Enteropathogenic Escherichia coli

“…In the case of EPEC, the LEE encoded type III secretion chaperone CesT was initially shown to bind and stabilize Tir within the bacterial cell (30,31); however, additional studies have demonstrated interactions with the effectors Map, EspF, and NleA (32)(33)(34). CesT is also required for the efficient in vitro type III secretion of other LEE and non-LEE type III effectors (33), suggesting that other chaperone-effector interactions may occur within the bacterium.…”