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Abstract
Type III secretion systems are complex nanomachines used for injection of proteins from Gram-negative bacteria into eukaryotic cells. While 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, next, effector proteins are injected. Hierarchy between these protein classes is mediated by a conserved gate-keeper protein, MxiC in Shigella. As its molecular mechanism of action is still poorly understood, we used its structure to guide site-directed mutagenesis and dissect its function. We identified mutants predominantly affecting all known features of MxiC regulation: 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.
Original language | English |
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Pages (from-to) | 1705-1723 |
Number of pages | 45 |
Journal | Journal of Biological Chemistry |
Volume | 292 |
Issue number | 5 |
Early online date | 14 Dec 2016 |
DOIs | |
Publication status | Published - 3 Feb 2017 |
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- 1 Finished
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Bacterial type III secretion systems: from structure to function
Blocker, A. J.
28/01/12 → 28/05/15
Project: Research