8AXN

Inner membrane ring and secretin N0 N1 domains of the type 3 secretion system of Shigella flexneri

This is a non-PDB format compatible entry.

Summary for 8AXN

• Entry DOI: 10.2210/pdb8axn/pdb
• Related: 6rwk 6rwx
• EMDB information: 10040 15702
• Descriptor: Protein MxiG, Lipoprotein MxiJ, Outer membrane protein MxiD (3 entities in total)
• Functional Keywords: type 3 secretion, inner membrane ring, secretin, shigella, infection, protein transport
• Biological source: Shigella flexneri; More
• Total number of polymer chains: 64
• Total formula weight: 2705988.20

Authors

Lunelli, M. (deposition date: 2022-08-31, release date: 2023-03-01, Last modification date: 2024-10-16)

Primary citation

Flacht, L.,Lunelli, M.,Kaszuba, K.,Chen, Z.A.,Reilly, F.J.O.,Rappsilber, J.,Kosinski, J.,Kolbe, M.
Integrative structural analysis of the type III secretion system needle complex from Shigella flexneri.
Protein Sci., 32:e4595-e4595, 2023

PubMed Abstract: The type III secretion system (T3SS) is a large, transmembrane protein machinery used by various pathogenic gram-negative bacteria to transport virulence factors into the host cell during infection. Understanding the structure of T3SSs is crucial for future developments of therapeutics that could target this system. However, much of the knowledge about the structure of T3SS is available only for Salmonella, and it is unclear how this large assembly is conserved across species. Here, we combined cryo-electron microscopy, cross-linking mass spectrometry, and integrative modeling to determine the structure of the T3SS needle complex from Shigella flexneri. We show that the Shigella T3SS exhibits unique features distinguishing it from other structurally characterized T3SSs. The secretin pore complex adopts a new fold of its C-terminal S domain and the pilotin MxiM[SctG] locates around the outer surface of the pore. The export apparatus structure exhibits a conserved pseudohelical arrangement but includes the N-terminal domain of the SpaS[SctU] subunit, which was not present in any of the previously published virulence-related T3SS structures. Similar to other T3SSs, however, the apparatus is anchored within the needle complex by a network of flexible linkers that either adjust conformation to connect to equivalent patches on the secretin oligomer or bind distinct surface patches at the same height of the export apparatus. The conserved and unique features delineated by our analysis highlight the necessity to analyze T3SS in a species-specific manner, in order to fully understand the underlying molecular mechanisms of these systems. The structure of the type III secretion system from Shigella flexneri delineates conserved and unique features, which could be used for the development of broad-range therapeutics.

PubMed: 36790757
DOI: 10.1002/pro.4595

Experimental method

ELECTRON MICROSCOPY (3.34 Å)