Supramolecular Structure of the Salmonella typhimurium Type III Protein Secretion System

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Science  24 Apr 1998:
Vol. 280, Issue 5363, pp. 602-605
DOI: 10.1126/science.280.5363.602

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The type III secretion system of Salmonella typhimuriumdirects the translocation of proteins into host cells. Evolutionarily related to the flagellar assembly machinery, this system is also present in other pathogenic bacteria, but its organization is unknown. Electron microscopy revealed supramolecular structures spanning the inner and outer membranes of flagellated and nonflagellated strains; such structures were not detected in strains carrying null mutations in components of the type III apparatus. Isolated structures were found to contain at least three proteins of this secretion system. Thus, the type III apparatus of S. typhimurium, and presumably other bacteria, exists as a supramolecular structure in the bacterial envelope.

  • * Present address: Structural Biology Center, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan.

  • To whom correspondence should be addressed. E-mail: galan{at}

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