7rye
From Proteopedia
Cryo-EM structure of the needle filament-tip complex of the Salmonella type III secretion injectisome
Structural highlights
FunctionSCTF1_SALTY Component of the type III secretion system (T3SS), also called injectisome, which is used to inject bacterial effector proteins into eukaryotic host cells (PubMed:12754250, PubMed:16501225, PubMed:30242280, PubMed:33750771). PrgI/SctF1 forms the external needle filament that protrudes from the bacterial surface (PubMed:12754250, PubMed:16501225, PubMed:22699623, PubMed:30242280, PubMed:31260457, PubMed:33750771). Is probably involved in the transduction of an activating signal, thought to be mediated by the distal tip of the needle filament, to the secretion machine (PubMed:31260457). Required for invasion of epithelial cells (PubMed:17617421). Required for the secretion of the effector protein SptP (PubMed:31260457, PubMed:33750771).[1] [2] [3] [4] [5] [6] [7] During infection, can induce innate immune responses (PubMed:24643544). The needle proteins interact with host TLR2 or TLR4, and induce signaling by NF-kappa-B and/or AP-1 (PubMed:24643544). This activation is MyD88 dependent and results in increased expression of cytokines, including TNF-alpha, IL-6 and IL-8 (PubMed:24643544).[8] Publication Abstract from PubMedType 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 approximately 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 membrane-embedded 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. Cryo-EM structure of the needle filament tip complex of the Salmonella type III secretion injectisome.,Guo EZ, Galan JE Proc Natl Acad Sci U S A. 2021 Nov 2;118(44):e2114552118. doi: , 10.1073/pnas.2114552118. PMID:34706941[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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