The structure of the Salmonella typhimurium type III secretion system needle shows divergence from the flagellar system.

TY - JOUR

T1 - The structure of the Salmonella typhimurium type III secretion system needle shows divergence from the flagellar system.

AU - Galkin, Vitold E

AU - Schmied, Wolfgang H

AU - Schraidt, Oliver

AU - Marlovits, Thomas

AU - Egelman, Edward H

PY - 2010

Y1 - 2010

N2 - The type III secretion system (T3SS) is essential for the infectivity of many pathogenic Gram-negative bacteria. The T3SS contains proteins that form a channel in the inner and outer bacterial membranes, as well as an extracellular needle that is used for transporting and injecting effector proteins into a host cell. The homology between the T3SS and the bacterial flagellar system has been firmly established, based upon both sequence similarities between respective proteins in the two systems and the structural homology of higher-order assemblies. It has previously been shown that the Shigella flexneri needle has a helical symmetry of approximately 5.6 subunits/turn, which is quite similar to that of the most intensively studied flagellar filament (from Salmonella typhimurium), which has approximately 5.5 subunits/turn. We now show that the Sa. typhimurium needle, expected by homology arguments to be more similar to the Sa. typhimurium flagellar filament than is the needle from Shigella, actually has approximately 6.3 subunits/turn. It is not currently understood how host cell contact, made at the tip of the needle, is communicated to the secretory system at the base. In contrast to the Sa. typhimurium flagellar filament, which shows a nearly crystalline order, the Sa. typhimurium needle has a highly variable symmetry, which could be used to transmit information about host cell contact.

AB - The type III secretion system (T3SS) is essential for the infectivity of many pathogenic Gram-negative bacteria. The T3SS contains proteins that form a channel in the inner and outer bacterial membranes, as well as an extracellular needle that is used for transporting and injecting effector proteins into a host cell. The homology between the T3SS and the bacterial flagellar system has been firmly established, based upon both sequence similarities between respective proteins in the two systems and the structural homology of higher-order assemblies. It has previously been shown that the Shigella flexneri needle has a helical symmetry of approximately 5.6 subunits/turn, which is quite similar to that of the most intensively studied flagellar filament (from Salmonella typhimurium), which has approximately 5.5 subunits/turn. We now show that the Sa. typhimurium needle, expected by homology arguments to be more similar to the Sa. typhimurium flagellar filament than is the needle from Shigella, actually has approximately 6.3 subunits/turn. It is not currently understood how host cell contact, made at the tip of the needle, is communicated to the secretory system at the base. In contrast to the Sa. typhimurium flagellar filament, which shows a nearly crystalline order, the Sa. typhimurium needle has a highly variable symmetry, which could be used to transmit information about host cell contact.

KW - Models, Molecular

KW - Protein Multimerization

KW - Cryoelectron Microscopy

KW - Bacterial Proteins/chemistry/physiology/ultrastructure

KW - Flagella/chemistry/ultrastructure

KW - Microscopy, Electron, Scanning Transmission

KW - Multiprotein Complexes/chemistry/ultrastructure

KW - Salmonella typhimurium/chemistry/physiology/ultrastructure

KW - Shigella flexneri/chemistry/ultrastructure

KW - Models, Molecular

KW - Protein Multimerization

KW - Cryoelectron Microscopy

KW - Bacterial Proteins/chemistry/physiology/ultrastructure

KW - Flagella/chemistry/ultrastructure

KW - Microscopy, Electron, Scanning Transmission

KW - Multiprotein Complexes/chemistry/ultrastructure

KW - Salmonella typhimurium/chemistry/physiology/ultrastructure

KW - Shigella flexneri/chemistry/ultrastructure

M3 - SCORING: Journal article

VL - 396

SP - 1392

EP - 1397

JO - J MOL BIOL

JF - J MOL BIOL

SN - 0022-2836

IS - 5

M1 - 5

ER -