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Arch Biochem Biophys. 2007 Dec 1;468(1):121-7. Epub 2007 Sep 29.

Enzymatic characterization of the enteropathogenic Escherichia coli type III secretion ATPase EscN.

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Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ap. Postal 70-243, México, DF 04510, Mexico.


Type III secretion is a transport mechanism by which bacteria secrete proteins across their cell envelope. This protein export pathway is used by two different bacterial nanomachines: the flagellum and the injectisome. An indispensable component of these secretion systems is an ATPase similar to the F1-ATPase beta subunit. Here we characterize EscN, an enteropathogenic Escherichia coli type III ATPase. A recombinant version of EscN, which was fully functional in complementation tests, was purified to homogeneity. Our results demonstrate that EscN is a Mg2+-dependent ATPase (kcat 0.35 s(-1)). We also define optimal conditions for the hydrolysis reaction. EscN displays protein concentration-dependent activity, suggesting that the specific activity changes with the oligomeric state of the protein. The presence of active oligomers was revealed by size exclusion chromatography and native gel electrophoresis.

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