Electrogeneicity of the lysosomal proton pump

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Abstract
Using acridine orange as a pH gradient probe, the effects of valinomycin and FCCP on the pH gradient across lysosomal membranes in an ATP‐free medium as well as on the rate of the inward ATP‐driven proton translocation were investigated. Both lysosome‐enriched and highly purified lysosomal preparations from rat liver were used with identical results. Ionophore effects were found to be different depending upon whether passive ion fluxes or ATP‐driven H+ translocation were involved and supported the existence of a membrane potential in the latter case. Anions stimulated the rate of ATP‐driven proton translocation and stimulation increased with increasing anion lipophilicity. These results strongly support the electrogenic nature of the lysosomal proton pump.