6F2D

A FliPQR complex forms the core of the Salmonella type III secretion system export apparatus.

Summary for 6F2D

• Entry DOI: 10.2210/pdb6f2d/pdb
• EMDB information: 4173
• Descriptor: Flagellar biosynthetic protein FliP, Flagellar biosynthetic protein FliR, Flagellar biosynthetic protein FliQ (3 entities in total)
• Functional Keywords: t3ss, flagella, cryo-em, export, membrane protein, protein transport
• Biological source: Salmonella enterica subsp. enterica; More
• Total number of polymer chains: 10
• Total formula weight: 205341.32

Authors

Johnson, S.,Kuhlen, L.,Abrusci, P.,Lea, S.M. (deposition date: 2017-11-24, release date: 2018-07-04, Last modification date: 2024-05-15)

Primary citation

Kuhlen, L.,Abrusci, P.,Johnson, S.,Gault, J.,Deme, J.,Caesar, J.,Dietsche, T.,Mebrhatu, M.T.,Ganief, T.,Macek, B.,Wagner, S.,Robinson, C.V.,Lea, S.M.
Structure of the core of the type III secretion system export apparatus.
Nat. Struct. Mol. Biol., 25:583-590, 2018

PubMed Abstract: Export of proteins through type III secretion systems is critical for motility and virulence of many major bacterial pathogens. Three putative integral membrane proteins (FliP, FliQ, FliR) are suggested to form the core of an export gate in the inner membrane, but their structure, assembly and location within the final nanomachine remain unclear. Here, we present the cryoelectron microscopy structure of the Salmonella Typhimurium FliP-FliQ-FliR complex at 4.2 Å. None of the subunits adopt canonical integral membrane protein topologies, and common helix-turn-helix structural elements allow them to form a helical assembly with 5:4:1 stoichiometry. Fitting of the structure into reconstructions of intact secretion systems, combined with cross-linking, localize the export gate as a core component of the periplasmic portion of the machinery. This study thereby identifies the export gate as a key element of the secretion channel and implies that it primes the helical architecture of the components assembling downstream.

PubMed: 29967543
DOI: 10.1038/s41594-018-0086-9

Experimental method

ELECTRON MICROSCOPY (4.2 Å)