7OSL

Cryo-EM structure of nonameric EPEC SctV-C

Summary for 7OSL

• Entry DOI: 10.2210/pdb7osl/pdb
• EMDB information: 13054
• Descriptor: Translocator EscV (1 entity in total)
• Functional Keywords: t3ss, sctv nonamer, export gate, protein transport
• Biological source: Escherichia coli O127:H6 (strain E2348/69 / EPEC)
• Total number of polymer chains: 9
• Total formula weight: 341572.11

Authors

Fahrenkamp, D.,Wald, J.,Yuan, B.,Marlovits, T.C. (deposition date: 2021-06-09, release date: 2021-09-29, Last modification date: 2024-07-17)

Primary citation

Yuan, B.,Portaliou, A.G.,Parakra, R.,Smit, J.H.,Wald, J.,Li, Y.,Srinivasu, B.,Loos, M.S.,Dhupar, H.S.,Fahrenkamp, D.,Kalodimos, C.G.,Duong van Hoa, F.,Cordes, T.,Karamanou, S.,Marlovits, T.C.,Economou, A.
Structural Dynamics of the Functional Nonameric Type III Translocase Export Gate.
J.Mol.Biol., 433:167188-167188, 2021

PubMed Abstract: Type III protein secretion is widespread in Gram-negative pathogens. It comprises the injectisome with a surface-exposed needle and an inner membrane translocase. The translocase contains the SctRSTU export channel enveloped by the export gate subunit SctV that binds chaperone/exported clients and forms a putative ante-chamber. We probed the assembly, function, structure and dynamics of SctV from enteropathogenic E. coli (EPEC). In both EPEC and E. coli lab strains, SctV forms peripheral oligomeric clusters that are detergent-extracted as homo-nonamers. Membrane-embedded SctV is necessary and sufficient to act as a receptor for different chaperone/exported protein pairs with distinct C-domain binding sites that are essential for secretion. Negative staining electron microscopy revealed that peptidisc-reconstituted His-SctV forms a tripartite particle of ∼22 nm with a N-terminal domain connected by a short linker to a C-domain ring structure with a ∼5 nm-wide inner opening. The isolated C-domain ring was resolved with cryo-EM at 3.1 Å and structurally compared to other SctV homologues. Its four sub-domains undergo a three-stage "pinching" motion. Hydrogen-deuterium exchange mass spectrometry revealed this to involve dynamic and rigid hinges and a hyper-flexible sub-domain that flips out of the ring periphery and binds chaperones on and between adjacent protomers. These motions are coincident with local conformational changes at the pore surface and ring entry mouth that may also be modulated by the ATPase inner stalk. We propose that the intrinsic dynamics of the SctV protomer are modulated by chaperones and the ATPase and could affect allosterically the other subunits of the nonameric ring during secretion.

PubMed: 34454944
DOI: 10.1016/j.jmb.2021.167188

Experimental method

ELECTRON MICROSCOPY (3.1 Å)