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Kubori, T, Sukhan, A, Aizawa, SI and Galán, JE (2000) Molecular characterization and assembly of the needle complex of the Salmonella typhimurium type III protein secretion system. Proc. Natl. Acad. Sci. U.S.A. 97:10225-30


Many bacterial pathogens of plants and animals have evolved a specialized protein-secretion system termed type III to deliver bacterial proteins into host cells. These proteins stimulate or interfere with host cellular functions for the pathogen's benefit. The Salmonella typhimurium pathogenicity island 1 encodes one of these systems that mediates this bacterium's ability to enter nonphagocytic cells. Several components of this type III secretion system are organized in a supramolecular structure termed the needle complex. This structure is made of discrete substructures including a base that spans both membranes and a needle-like projection that extends outward from the bacterial surface. We demonstrate here that the type III secretion export apparatus is required for the assembly of the needle substructure but is dispensable for the assembly of the base. We show that the length of the needle segment is determined by the type III secretion associated protein InvJ. We report that InvG, PrgH, and PrgK constitute the base and that PrgI is the main component of the needle of the type III secretion complex. PrgI homologs are present in type III secretion systems from bacteria pathogenic for animals but are absent from bacteria pathogenic for plants. We hypothesize that the needle component may establish the specificity of type III secretion systems in delivering proteins into either plant or animal cells.


PubMed PMC27824 Online version:10.1073/pnas.170128997


Amino Acid Sequence; Antigens, Bacterial; Bacterial Proteins/chemistry; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Cell Membrane/physiology; Cell Membrane/ultrastructure; Membrane Transport Proteins; Molecular Sequence Data; Salmonella typhimurium/genetics; Salmonella typhimurium/pathogenicity; Salmonella typhimurium/physiology; Salmonella typhimurium/ultrastructure; Sequence Alignment; Sequence Homology, Amino Acid; Virulence/genetics



Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status


GO:0016021: integral component of membrane



Figure 1 shows the difference between the wild type the mutated InvA protein which leads to a change in the needle complex formed by the type III secretion protein-export mechanism found in S. typhimurium.

CACAO 12433


GO:0030257: type III protein secretion system complex



"All strains were derived from the nonflagellated S. typhimurium strain SJW2941" InvG, PrgH, and PrgK Are Components of the Base Substructure of the Needle Complex. Fig 2

CACAO 12448


GO:0008565: protein transporter activity



Molecular characterization and assembly of the needle complex of the Salmonella typhimurium type III protein secretion system. Kubori et al. (2000) In this paper the authors isolate, purify and determine that PrgI is the main subunit of the T3SS

CACAO 12577


See also


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