title: Enzymatic characterization of the enteropathogenic Escherichia coli type III secretion ATPase EscN.
abstract: 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.
authors.affiliation: Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ap. Postal 70-243, México, DF 04510, Mexico.
authors.forename: Angel
authors.initials: A
authors.lastname: Andrade
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Pardo
authors.forename: Norma
authors.initials: N
authors.lastname: Espinosa
authors.forename: Gerardo
authors.initials: G
authors.lastname: Pérez-Hernández
authors.forename: Bertha
authors.initials: B
authors.lastname: González-Pedrajo
mesh_terms: D001693:Biological Transport, Active / Q000502:physiology; D017301:Ca(2+) Mg(2+)-ATPase / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D017301:Ca(2+) Mg(2+)-ATPase