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SycE allows secretion of YopE–DHFR hybrids by the Yersinia enterocolitica type III Ysc system
Author(s) -
Feldman Mario F.,
Müller Simone,
Wüest Esther,
Cornelis Guy R.
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.1365-2958.2002.03241.x
Subject(s) - secretion , effector , chaperone (clinical) , biology , type three secretion system , mutant , secretory protein , microbiology and biotechnology , yersinia enterocolitica , virulence , biochemistry , genetics , bacteria , gene , medicine , pathology
Summary The Ysc type III secretion system allows Yersinia enterocolitica to translocate virulence proteins, called Yop effectors, into the cytosol of eukaryotic cells. Some of the Yop effectors possess an individual chaperone called a Syc protein. The first 15 amino acids of the YopE effector constitute a secretion signal that is sufficient to promote secretion of several reporter proteins. Residues 15–50 of YopE comprise the minimal binding domain for the SycE chaperone. In this study, we investigated the secretion by the Ysc system of several YopE–DHFR hybrid proteins with different folding properties, and evaluated the role of SycE, the cognate chaperone of YopE, in this context. We have analysed the secretion of hybrids containing 16 (YopE 16 ), 52 (YopE 52 ) and 80 (the complete region covered by the chaperone, YopE 80 ) amino acids of YopE or full‐length YopE (YopE FL ) with wild‐type DHFR and two mutants with altered folding properties. The hybrids containing DHFRΔ77, the mutant whose folding properties are the most drastically affected, could be secreted in all the conditions tested, even in the absence of the chaperone SycE. In contrast, DHFRwt could only be secreted fused to the first 52 amino acids of YopE, and its secretion was strictly dependent on SycE. The hybrids YopE 80 –DHFRwt and YopE FL –DHFRwt were not secreted. YopE FL –DHFRwt completely jammed the channel in an SycE‐dependent fashion. Our experiments indicate that, in order to be secreted, proteins must be unfolded or only partially folded, and that TSS chaperones could keep their substrates in a secretion‐competent conformation, probably by preventing their folding. In addition, they show that the secretion apparatus can reject folded proteins if they are not deeply engaged into the injectisome.