Evidence for a high proton translocation stoichiometry of the H+-ATPase complex in well coupled proteoliposomes reconstituted from a thermophilic cyanobacterium

AbstractEvidence is presented for a high proton translocation stoichiometry (H+/ATP) of approx. 9 in ATPase proteoliposomes with extremely low permeability for ions, reconstituted from a thermophilic cyanobacterium. A proportional relation between the phosphate potential (ΔGfp) and the proton-motive force (Δp) was observed in thermodynamic equilibrium. A bulk-to-bulk Δp was imposed by valinomycin-induced K− diffusion potentials of different size while the initial ΔGfp was varied. In all cases equilibrium was reached in about 1.5 h. A high H−/ATP ratio was also deduced from the relation between the initial rates of ATP synthesis or hydrolysis at varying ΔGfp and Δp. The implications of these results for the mechanism of energy transduction in energy-conserving membranes are discussed