biostudies-literatureSpreter TNIAID NIH HHSNIGMS NIH HHS468-76https://www.ebi.ac.uk/biostudies/studies/S-EPMC2860953biostudies-literatureUnknown16(5)The type III secretion system (T3SS) is a macromolecular 'injectisome' that allows bacterial pathogens to transport virulence proteins into the eukaryotic host cell. This macromolecular complex is composed of connected ring-like structures that span both bacterial membranes. The crystal structures of the periplasmic domain of the outer membrane secretin EscC and the inner membrane protein PrgH reveal the conservation of a modular fold among the three proteins that form the outer membrane and inner membrane rings of the T3SS. This leads to the hypothesis that this conserved fold provides a common ring-building motif that allows for the assembly of the variably sized outer membrane and inner membrane rings characteristic of the T3SS. Using an integrated structural and experimental approach, Nature structural & molecular biologyA conserved structural motif mediates formation of the periplasmic rings in the type III secretion system.PMC2860953P20 GM076222R01 AI030479U54 AI057141U54 AI05741Spreter TKimbrough TGBaker DPfuetzner RAMiller SIVuckovic MStrynadka NCYip CKAndre ISanowar SDeng WYu ACFinlay BBfalseA conserved structural motif mediates formation of the periplasmic rings in the type III secretion system.The type III secretion system (T3SS) is a macromolecular 'injectisome' that allows bacterial pathogens to transport virulence proteins into the eukaryotic host cell. This macromolecular complex is composed of connected ring-like structures that span both bacterial membranes. The crystal structures of the periplasmic domain of the outer membrane secretin EscC and the inner membrane protein PrgH reveal the conservation of a modular fold among the three proteins that form the outer membrane and inner membrane rings of the T3SS. This leads to the hypothesis that this conserved fold provides a common ring-building motif that allows for the assembly of the variably sized outer membrane and inner membrane rings characteristic of the T3SS. Using an integrated structural and experimental approach, 2009-01-01T00:00:00Z2009 May2026-05-04T10:58:04.372Z2019-03-27T00:30:24ZS-EPMC28609531939617010.1038/nsmb.1603