Structural insights into the assembly of the type III secretion needle complex.

Marlovits, Thomas C; Kubori, Tomoko; Sukhan, Anand; Thomas, Dennis R; Galán, Jorge E; Unger, Vinzenz M · Science · 2004

basic_science · Level V

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Abstract

Type III secretion systems (TTSSs) mediate translocation of virulence factors into host cells. We report the 17-angstrom resolution structures of a central component of Salmonella typhimurium TTSS, the needle complex, and its assembly precursor, the bacterial envelope-anchored base. Both the base and the fully assembled needle complex adopted multiple oligomeric states in vivo, and needle assembly was accompanied by recruitment of the protein PrgJ as a structural component of the base. Moreover, conformational changes during needle assembly created scaffolds for anchoring both PrgJ and the needle substructure and may provide the basis for substrate-specificity switching during type III secretion.

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