| Zdroj: |
Roehrich, A D, Bordignon, E, Mode, S, Da-kang, S, Liu, X, Pain, M, Murillo, I, Martinez-Argudo, I, Sessions, R B & Blocker, A J 2017, ' Steps for Shigella Gatekeeper MxiC Function in Hierarchical Type III Secretion Regulation ', Journal of Biological Chemistry, vol. 292, no. 5, pp. 1705-1723 . https://doi.org/10.1074/jbc.M116.746826 |
| Popis: |
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. |
