title: Physiology of the Vc-NhaP paralogous group of cation-proton antiporters in Vibrio cholerae.
abstract: The genome of Vibrio cholerae encodes three cation-proton antiporters of NhaP-type, Vc-NhaP1, 2, and 3. To examine physiological roles of Vc-NhaP antiporters, triple ΔnhaP1ΔnhaP2ΔnhaP3 and single ΔnhaP3 deletion mutants of V. cholerae were constructed and characterized. Vc-NhaP3 was, for the first time, cloned and biochemically characterized. Activity measurements on the inside-out membrane vesicle experimental model defined Vc-NhaP3 as a potassium-specific cation-proton antiporter. While elimination of functional Vc-NhaP3 resulted in only minor growth defect in potassium-rich medium at pH 6.0, the triple Vc-NhaP mutant demonstrated severe growth defects at both low and high [K+] at pH 6.0 and failed to grow at high [K+] in mildly alkaline (pH 8.0 and 8.5) media, as well. Expressed from a plasmid, neither of the Vc-NhaP paralogues was able to complement the severe potassium-sensitive phenotype of the triple deletion mutant completely. Vc-NhaP1 provided much better complementation at acidic pH compared to Vc-NhaP2, despite the fact that Vc-NhaP2 showed much higher antiport activity in sub-bacterial vesicles. In mildly alkaline pH only Vc-NhaP2 complemented the potassium-sensitive phenotype of the triple deletion mutant. Taken together, these data suggest that in vivo all three isoforms operate in concert, contributing to K+resistance of V. cholerae. We suggest that the Vc-NhaP paralogue group might play a role in passing gastric acid barrier by ingested V. cholerae cells.
authors.affiliation: Department of Microbiology, Faculty of Science, University of Manitoba, Rm. 430 Buller Building, Winnipeg, MB, R3T 2N2, Canada.
authors.forename: Muntahi
authors.initials: M
authors.lastname: Mourin
authors.affiliation: Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Carla B
authors.initials: CB
authors.lastname: Schubiger
authors.affiliation: Department of Microbiology, Faculty of Science, University of Manitoba, Rm. 430 Buller Building, Winnipeg, MB, R3T 2N2, Canada.
authors.forename: Craig T
authors.initials: CT
authors.lastname: Resch
authors.affiliation: Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: Claudia C
authors.initials: CC
authors.lastname: Häse
authors.affiliation: Department of Microbiology, Faculty of Science, University of Manitoba, Rm. 430 Buller Building, Winnipeg, MB, R3T 2N2, Canada. Pavel.Dibrov@ad.umanitoba.ca.
authors.forename: Pavel
authors.initials: P
authors.lastname: Dibrov
mesh_terms: D017920:Antiporters / Q000235:genetics* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D003470:Culture Media / Q000737:chemistry; D017353:Gene Deletion; D006863:Hydrogen-Ion Concentration; D011188:Potassium / Q000378:metabolism; D014734:Vibrio cholerae / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
chemical_list: D017920:Antiporters; D001426:Bacterial Proteins; D003470:Culture Media; D011188:Potassium
keywords: Cation–proton antiporters; NhaP; Potassium resistance; Vibrio cholerae