A H+-gated urea channel: The link between Helicobacter pylori urease and gastric colonization

Acidic media trigger cytoplasmic urease activity of the unique human gastri c pathogen Helicobacter pylori. Deletion of urel prevents this activation o f cytoplasmic urease that is essential for bacterial acid resistance. Urel is an inner membrane protein with six transmembrane segments as shown by in vitro transcription/translation and membrane separation. Expression of Ure l in Xenopus oocytes results in acid-stimulated urea uptake, with a pH prof ile similar to activation of cytoplasmic urease, Mutation of periplasmic hi stidine 123 abolishes stimulation. Urel-mediated transport is urea specific , passive, nonsaturable, nonelectrogenic, and temperature independent. Urel functions as a H+-gated urea channel regulating cytoplasmic urease that is essential for gastric survival and colonization.