7AGX

Apo-state type 3 secretion system export apparatus complex from Salmonella enterica typhimurium

This is a non-PDB format compatible entry.

Summary for 7AGX

• Entry DOI: 10.2210/pdb7agx/pdb
• EMDB information: 11780
• Descriptor: Surface presentation of antigens protein SpaP, Surface presentation of antigens protein SpaR, Surface presentation of antigens protein SpaQ, ... (5 entities in total)
• Functional Keywords: t3ss, export apparatus, injectisome, needle complex, protein transport
• Biological source: Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720); More
• Total number of polymer chains: 33
• Total formula weight: 408509.73

Authors

Goessweiner-Mohr, N.,Fahrenkamp, D.,Miletic, S.,Wald, J.,Marlovits, T. (deposition date: 2020-09-23, release date: 2021-03-17, Last modification date: 2024-05-01)

Primary citation

Miletic, S.,Fahrenkamp, D.,Goessweiner-Mohr, N.,Wald, J.,Pantel, M.,Vesper, O.,Kotov, V.,Marlovits, T.C.
Substrate-engaged type III secretion system structures reveal gating mechanism for unfolded protein translocation.
Nat Commun, 12:1546-1546, 2021

PubMed Abstract: Many bacterial pathogens rely on virulent type III secretion systems (T3SSs) or injectisomes to translocate effector proteins in order to establish infection. The central component of the injectisome is the needle complex which assembles a continuous conduit crossing the bacterial envelope and the host cell membrane to mediate effector protein translocation. However, the molecular principles underlying type III secretion remain elusive. Here, we report a structure of an active Salmonella enterica serovar Typhimurium needle complex engaged with the effector protein SptP in two functional states, revealing the complete 800Å-long secretion conduit and unraveling the critical role of the export apparatus (EA) subcomplex in type III secretion. Unfolded substrates enter the EA through a hydrophilic constriction formed by SpaQ proteins, which enables side chain-independent substrate transport. Above, a methionine gasket formed by SpaP proteins functions as a gate that dilates to accommodate substrates while preventing leaky pore formation. Following gate penetration, a moveable SpaR loop first folds up to then support substrate transport. Together, these findings establish the molecular basis for substrate translocation through T3SSs and improve our understanding of bacterial pathogenicity and motility.

PubMed: 33750771
DOI: 10.1038/s41467-021-21143-1

Experimental method

ELECTRON MICROSCOPY (3.6 Å)