Experimental Verification of a Sequence-Based Prediction: F 1 F 0 -Type ATPase of Vibrio cholerae Transports Protons, Not Na + Ions

Abstract

ABSTRACT The membrane energetics of the intestinal pathogen Vibrio cholerae involves both H + and Na + as coupling ions. The sequence of the c subunit of V. cholerae F 0 F 1 ATPase suggested that this enzyme is H + specific, in contrast to the results of previous studies on the Na + -dependent ATP synthesis in closely related Vibrio spp. Measurements of the pH gradient and membrane potential in membrane vesicles isolated from wild-type and Δ atpE mutant V. cholerae show that the F 1 F 0 ATPase of V. cholerae is an H + , not Na + , pump, confirming the bioinformatics assignments that were based on the Na + -binding model of S. Rahlfs and V. Müller (FEBS Lett. 404: 269-271, 1999). Application of this model to the AtpE sequences from other bacteria and archaea indicates that Na + -specific F 1 F 0 ATPases are present in a number of important bacterial pathogens.