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Interplay between predicted inner‐rod and gatekeeper in controlling substrate specificity of the type III secretion system
Author(s) -
Cherradi Youness,
Schiavolin Lionel,
Moussa Simon,
Meghraoui Alaeddine,
Meksem Ahmed,
Biskri Latéfa,
Azarkan Mohamed,
Allaoui Abdelmounaaïm,
Botteaux Anne
Publication year - 2013
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 - 10.1111/mmi.12158
Subject(s) - secretion , effector , biology , microbiology and biotechnology , cytoplasm , chaperone (clinical) , virulence , type three secretion system , mutant , yersinia , phenotype , secretory protein , genetics , bacteria , gene , biochemistry , medicine , pathology
Summary The type III secretion apparatus ( T 3 SA ) is a multi‐protein complex central to the virulence of many G ram‐negative pathogens. Currently, the mechanisms controlling the hierarchical addressing of needle subunits, translocators and effectors to the T 3 SA are still poorly understood. In S higella, MxiC is known to sequester effectors within the cytoplasm prior to receiving the activation signal from the needle. However, molecules involved in linking the needle and MxiC are unknown. Here, we demonstrate a molecular interaction between MxiC and the predicted inner‐rod component MxiI suggesting that this complex plugs the T 3 SA entry gate. Our results suggest that MxiI – MxiC complex dissociation facilitates the switch in secretion from translocators to effectors. We identified MxiC F 206 S variant, unable to interact with MxiI , which exhibits a constitutive secretion phenotype although it remains responsive to induction. Moreover, we identified the mxiI Q67A mutant that only secretes translocators, a phenotype that was suppressed by coexpression of the MxiC F 206 S variant. We demonstrated the interaction between MxiI and MxiC homologues in Y ersinia and S almonella . Lastly, we identified an interaction between MxiC and chaperone IpgC which contributes to understanding how translocators secretion is regulated. In summary, this study suggests the existence of a widely conserved T 3 S mechanism that regulates effectors secretion.