Induction of Transmembrane Proton Transfer by Mercurials in Mitochondria

The ion movements accompanying the mercurial-induced energized ejection of protons in beef heart mitochondria have been analyzed. These are of two kinds: symport movement of anions (as yet unidentified) and antiport movement of monovalent cations such as potassium. Thus in the massive energized ejection of protons induced by fluorescein mercuric acetate, the molar ratio of potassium ion taken up to proton released (potassium to proton ratio) is about 0.2. This ratio has been shown to reflect a balance between two processes: potassium-proton exchange with a ratio of 1.0 and extrusion of potassium and a chaotropic anion simultaneous with the exchange which can in the limit lower the ratio to 0. The nature of the ion movements accompanying the energized proton ejection induced by gramicidin can be modified by variation in the concentration of ionophore. At low concentration potassium-proton exchange predominates (K+:H+ ratio close to 1), whereas at higher concentrations, both symport and antiport ion movements take place (K+:H+ ratio about 0.2). It has been concluded that the induction of proton ejection by fluorescein mercuric acetate involves the release in the membrane phase of an ionophore specific for monovalent cations which permits proton-potassium exchange. When this exchange cannot take place for lack of an ionophore, energized proton release is interdicted. The induction of endogenous ionophore by fluorescein mercuric acetate permits not only energized, but also nonenergized potassium-proton exchange.