Steps for Shigella Gatekeeper Protein MxiC Function in Hierarchical Type III Secretion Regulation

Article Article scientifique Article Steps for Shigella Gatekeeper Protein MxiC Function in Hierarchical Type III Secretion Regulation eng 2017-02 author Roehrich A. Dorothea author Bordignon Enrica 0000-0003-2450-5161 973830 Département de chimie physique (CHIFI) author Mode Selma author Shen Da-Kang author Liu Xia author Pain Maria author Murillo Caballero Maria Isabel 519417 author Martinez-Argudo Isabel 0000-0001-5067-1791 author Sessions Richard B. author Blocker Ariel J. 0000-0002-8705-2641 1705-1723 10.1074/jbc.M116.746826 27974466 0021-9258 PMC5290946 https://linkinghub.elsevier.com/retrieve/pii/S0021925820367016 Type III secretion systems are complex nanomachines used for injection of proteins from Gram-negative bacteria into eukaryotic cells. Although they are assembled when the environmental conditions are appropriate, they only start secreting upon contact with a host cell. Secretion is hierarchical. First, the pore-forming translocators are released. Second, effector proteins are injected. Hierarchy between these protein classes is mediated by a conserved gatekeeper protein, MxiC, in Shigella. As its molecular mechanism of action is still poorly understood, we used its structure to guide site-directed mutagenesis and to dissect its function. We identified mutants predominantly affecting all known features of MxiC regulation as follows: secretion of translocators, MxiC and/or effectors. Using molecular genetics, we then mapped at which point in the regulatory cascade the mutants were affected. Analysis of some of these mutants led us to a set of electron paramagnetic resonance experiments that provide evidence that MxiC interacts directly with IpaD. We suggest how this interaction regulates a switch in its conformation that is key to its functions. Gram-negative bacteria MxiC Shigella Biophysics Cellular regulation Electron paramagnetic resonance (EPR) Molecular genetics Protein secretion Type III secretion system (T3SS) University of Bristol Senior Research Fellowship Medical Research Council MR/J002097/1 Freie UniversitÃ¤t Berlin Research support Wellcome Trust WT088266 true The Journal of biological chemistry 292 5 3e2850c9-3df1-45b5-8e6d-cf4c05962fd7 Article (Published version) Public Article-scientifique-from-unpaywall.pdf 3404835 application/pdf CC BY 6232ee87aea1dbcabd4cf8302c4c44471228d99aff29c95fd70e37a4f6c4a772 openAccess

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Steps for Shigella Gatekeeper Protein MxiC Function in Hierarchical Type III Secretion Regulation	The Journal of biological chemistry			2017	78	17

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Murillo Caballero, Maria Isabel