A 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, we generated ring models for the periplasmic domain of EscC and placed them in the context of the assembled T3SS, providing evidence for direct interaction between the outer membrane and inner membrane ring components and an unprecedented span of the outer membrane secretin.
Spreter
Thomas
T
Department of Biochemistry and Molecular Biology and the Center for Blood Research, University of British Columbia, Vancouver, Canada.
Yip
Calvin K
CK
Sanowar
Sarah
S
André
Ingemar
I
Kimbrough
Tyler G
TG
Vuckovic
Marija
M
Pfuetzner
Richard A
RA
Deng
Wanyin
W
Yu
Angel C
AC
Finlay
B Brett
BB
Baker
David
D
Miller
Samuel I
SI
Strynadka
Natalie C J
NC
D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D019897:Periplasm / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012486:Salmonella typhimurium / Q000472:pathogenicity*; D012633:Secretin / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D037521:Virulence Factors / Q000737:chemistry* / Q000378:metabolism*
D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; C079790:PrgH protein, Salmonella typhimurium; D037521:Virulence Factors; C090991:invG protein, Salmonella typhimurium; D012633:Secretin