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Composition and Biophysical Properties of the Sorting Platform Pods in the Shigella Type III Secretion System

Shigella flexneri, causative agent of bacillary dysentery (shigellosis), uses a type III secretion system (T3SS) as its primary virulence factor. The T3SS injectisome delivers effector proteins into host cells to promote entry and create an important intracellular niche. The injectisome’s cytoplasmi...

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Autores principales: Tachiyama, Shoichi, Skaar, Ryan, Chang, Yunjie, Carroll, Brittany L., Muthuramalingam, Meenakumari, Whittier, Sean K., Barta, Michael L., Picking, Wendy L., Liu, Jun, Picking, William D.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8211105/
https://www.ncbi.nlm.nih.gov/pubmed/34150677
http://dx.doi.org/10.3389/fcimb.2021.682635
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author Tachiyama, Shoichi
Skaar, Ryan
Chang, Yunjie
Carroll, Brittany L.
Muthuramalingam, Meenakumari
Whittier, Sean K.
Barta, Michael L.
Picking, Wendy L.
Liu, Jun
Picking, William D.
author_facet Tachiyama, Shoichi
Skaar, Ryan
Chang, Yunjie
Carroll, Brittany L.
Muthuramalingam, Meenakumari
Whittier, Sean K.
Barta, Michael L.
Picking, Wendy L.
Liu, Jun
Picking, William D.
author_sort Tachiyama, Shoichi
collection PubMed
description Shigella flexneri, causative agent of bacillary dysentery (shigellosis), uses a type III secretion system (T3SS) as its primary virulence factor. The T3SS injectisome delivers effector proteins into host cells to promote entry and create an important intracellular niche. The injectisome’s cytoplasmic sorting platform (SP) is a critical assembly that contributes to substrate selection and energizing secretion. The SP consists of oligomeric Spa33 “pods” that associate with the basal body via MxiK and connect to the Spa47 ATPase via MxiN. The pods contain heterotrimers of Spa33 with one full-length copy associated with two copies of a C-terminal domain (Spa33(C)). The structure of Spa33(C) is known, but the precise makeup and structure of the pods in situ remains elusive. We show here that recombinant wild-type Spa33 can be prepared as a heterotrimer that forms distinct stable complexes with MxiK and MxiN. In two-hybrid analyses, association of the Spa33 complex with these proteins occurs via the full-length Spa33 component. Furthermore, these complexes each have distinct biophysical properties. Based on these properties, new high-resolution cryo-electron tomography data and architectural similarities between the Spa33 and flagellar FliM-FliN complexes, we provide a preliminary model of the Spa33 heterotrimers within the SP pods. From these findings and evolving models of SP interfaces and dynamics in the Yersinia and Salmonella T3SS, we suggest a model for SP function in which two distinct complexes come together within the context of the SP to contribute to form the complete pod structures during the recruitment of T3SS secretion substrates.
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spelling pubmed-82111052021-06-18 Composition and Biophysical Properties of the Sorting Platform Pods in the Shigella Type III Secretion System Tachiyama, Shoichi Skaar, Ryan Chang, Yunjie Carroll, Brittany L. Muthuramalingam, Meenakumari Whittier, Sean K. Barta, Michael L. Picking, Wendy L. Liu, Jun Picking, William D. Front Cell Infect Microbiol Cellular and Infection Microbiology Shigella flexneri, causative agent of bacillary dysentery (shigellosis), uses a type III secretion system (T3SS) as its primary virulence factor. The T3SS injectisome delivers effector proteins into host cells to promote entry and create an important intracellular niche. The injectisome’s cytoplasmic sorting platform (SP) is a critical assembly that contributes to substrate selection and energizing secretion. The SP consists of oligomeric Spa33 “pods” that associate with the basal body via MxiK and connect to the Spa47 ATPase via MxiN. The pods contain heterotrimers of Spa33 with one full-length copy associated with two copies of a C-terminal domain (Spa33(C)). The structure of Spa33(C) is known, but the precise makeup and structure of the pods in situ remains elusive. We show here that recombinant wild-type Spa33 can be prepared as a heterotrimer that forms distinct stable complexes with MxiK and MxiN. In two-hybrid analyses, association of the Spa33 complex with these proteins occurs via the full-length Spa33 component. Furthermore, these complexes each have distinct biophysical properties. Based on these properties, new high-resolution cryo-electron tomography data and architectural similarities between the Spa33 and flagellar FliM-FliN complexes, we provide a preliminary model of the Spa33 heterotrimers within the SP pods. From these findings and evolving models of SP interfaces and dynamics in the Yersinia and Salmonella T3SS, we suggest a model for SP function in which two distinct complexes come together within the context of the SP to contribute to form the complete pod structures during the recruitment of T3SS secretion substrates. Frontiers Media S.A. 2021-06-03 /pmc/articles/PMC8211105/ /pubmed/34150677 http://dx.doi.org/10.3389/fcimb.2021.682635 Text en Copyright © 2021 Tachiyama, Skaar, Chang, Carroll, Muthuramalingam, Whittier, Barta, Picking, Liu and Picking https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Cellular and Infection Microbiology
Tachiyama, Shoichi
Skaar, Ryan
Chang, Yunjie
Carroll, Brittany L.
Muthuramalingam, Meenakumari
Whittier, Sean K.
Barta, Michael L.
Picking, Wendy L.
Liu, Jun
Picking, William D.
Composition and Biophysical Properties of the Sorting Platform Pods in the Shigella Type III Secretion System
title Composition and Biophysical Properties of the Sorting Platform Pods in the Shigella Type III Secretion System
title_full Composition and Biophysical Properties of the Sorting Platform Pods in the Shigella Type III Secretion System
title_fullStr Composition and Biophysical Properties of the Sorting Platform Pods in the Shigella Type III Secretion System
title_full_unstemmed Composition and Biophysical Properties of the Sorting Platform Pods in the Shigella Type III Secretion System
title_short Composition and Biophysical Properties of the Sorting Platform Pods in the Shigella Type III Secretion System
title_sort composition and biophysical properties of the sorting platform pods in the shigella type iii secretion system
topic Cellular and Infection Microbiology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8211105/
https://www.ncbi.nlm.nih.gov/pubmed/34150677
http://dx.doi.org/10.3389/fcimb.2021.682635
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