1. Steps for Shigella Gatekeeper Protein MxiC Function in Hierarchical Type III Secretion Regulation.
- Author
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Roehrich AD, Bordignon E, Mode S, Shen DK, Liu X, Pain M, Murillo I, Martinez-Argudo I, Sessions RB, and Blocker AJ
- Subjects
- Antigens, Bacterial genetics, Antigens, Bacterial metabolism, Bacterial Proteins genetics, Bacterial Proteins metabolism, Bacterial Secretion Systems genetics, Mutation, Shigella flexneri genetics, Bacterial Secretion Systems metabolism, Shigella flexneri metabolism
- Abstract
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., (© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)
- Published
- 2017
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