期刊
出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2114552118
关键词
bacterial pathogenesis; structural biology; cryoelectron microscopy; protein secretion; organelle assembly
资金
- NIH [AI030492]
Type III secretion systems are multiprotein molecular machines essential for the virulence of bacterial pathogens. The injectisome mediates the delivery of bacterially encoded proteins into eukaryotic target cells. The structure of the needle tip complex and its interaction with the needle filament are crucial for the translocation of effector proteins.
Type III secretion systems are multiprotein molecular machines required for the virulence of several important bacterial pathogens. The central element of these machines is the injectisome, a similar to 5-Md multiprotein structure that mediates the delivery of bacterially encoded proteins into eukaryotic target cells. The injectisome is composed of a cytoplasmic sorting platform, and a membraneembedded needle complex, which is made up of a multiring base and a needle-like filament that extends several nanometers from the bacterial surface. The needle filament is capped at its distal end by another substructure known as the tip complex, which is crucial for the translocation of effector proteins through the eukaryotic cell plasma membrane. Here we report the cryo-EM structure of the Salmonella Typhimurium needle tip complex docked onto the needle filament tip. Combined with a detailed analysis of structurally guided mutants, this study provides major insight into the assembly and function of this essential component of the type III secretion protein injection machine.
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