Control of respiration in sonicated cytochrome oxidase proteoliposomes by gated and ungated ionophores.

Respiration of cytochrome oxidase-containing sonicated proteoliposomes is partially stimulated by nigericin or by alamethicin. Valinomycin at low concentrations fully releases the nigericin-dependent respiration but inhibits the alamethicin-dependent respiration. Respiratory stimulation by the gated ionophore alamethicin must occur in the face of a continuing membrane potential; stimulation by nigericin is accompanied by an increase in the measured membrane potential. We conclude that delta pH rather than delta psi may be the main source of respiratory control in our type of proteoliposomes.