Current-voltage characteristics of the proton pump atChara plasmalemma: I. pH dependence

A feature of the current-voltage (I/V) and conductance-voltage (G/V) characteristics is described, which can be attributed to the action of the proton pump at the Chara plasmalemma. The study of pH dependence in the range 4.5 to 11.0 and exposure to metabolic inhibitors confirm the pump involvement. A model describing kinetics of H+-extruding ATPase (Hansen, U.-P., Gradmann, D., Sanders, D., Slayman, C.L. 1981. J. Membrane Biol. 63:165-190) is fitted to the data yielding the I/V and G/V relationships of the Chara proton pump. The results show that the stoichiometry is 1H + : 1ATP.