The cytoplasmic domain of MxiG interacts with MxiK and directs assembly of the sorting platform in the Shigella type III secretion system
| Autor: | Michael L. Barta, Bo Hu, Jun Liu, Meenakumari Muthuramalingam, William D. Picking, Yunjie Chang, Shoichi Tachiyama, Wendy L. Picking |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
0301 basic medicine
030102 biochemistry & molecular biology Effector Chemistry Sorting Cell Biology Biochemistry Interactome Type three secretion system Protein–protein interaction Cell biology Insertional mutagenesis 03 medical and health sciences 030104 developmental biology Basal body Secretion Molecular Biology |
| Zdroj: | Journal of Biological Chemistry. 294:19184-19196 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.ra119.009125 |
| Popis: | Many Gram-negative bacteria use type III secretion systems (T3SSs) to inject virulence effector proteins into eukaryotic cells. The T3SS apparatus (T3SA) is structurally conserved among diverse bacterial pathogens and consists of a cytoplasmic sorting platform, an envelope-spanning basal body, and an extracellular needle with tip complex. The sorting platform is essential for effector recognition and powering secretion. Studies using bacterial "minicells" have revealed an unprecedented level of structural detail of the sorting platform; however, many of the structure-function relationships within this complex remain enigmatic. Here, we report on improved cryo-electron tomographic approaches to enhance the resolution of the Shigella T3SA sorting platform (at ≤2 nm resolution) done in concert with biochemical and genetic methods to define the sorting platform interactome and interactions with the T3SA inner membrane ring (IR). We observed that the sorting platform consists of "pods" with 6-fold symmetry that interact with the Spa47 ATPase via radial extensions comprising MxiN. Most importantly, MxiK maintained an interaction with the IR via specific interactions with the cytoplasmic domain of the IR protein MxiG (MxiGC), which is a noncanonical forkhead-associated domain, and MxiK has an elongated structure that interacts with the IR via MxiGC. T4 lysozyme-mediated insertional mutagenesis of MxiK revealed its orientation within the sorting platform and enabled disruption of interactions with its binding partners, which abolished sorting platform assembly. Finally, a comparison with the homologous interactions in the Salmonella T3SS sorting platform revealed clear differences in their IR-sorting platform interfaces that have possible mechanistic implications. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|