Proton electrochemical gradient and phosphate potential in submitochondrial particles

Abstract

1. The aerobic uptake of inorganic ions, such as 86Rb + or 125I −, by submitochondrial particles, is about one order of magnitude lower than the uptake of organic ions, such as acridines or 8-anilino-1-naphthalene sulphonate. The values of ΔpH, the transmembrane pH differential, and Δψ, the transmembrane membrane potential are between 60 and 100 mV when calculated on the inorganic ions and between 150 and 240 mV when calculated on the organic ions. The discrepancy between the ΔpH and Δψ values from organic and inorganic ions is large at high but not at low ion/protein ratios. 2. In the absence of weak bases and strong acids the values of Δ \\ ̃ gm H , the proton electrochemical potential difference, are close to 100 mV and the magnitude of ΔpH and Δψ are similar. Weak bases decrease ΔpH and enhance Δψ. Strong acids decrease Δψ and enhance ΔpH. Interchangeability of ΔpH with Δψ occurs at low concentrations of weak bases and strong acids. High concentrations of weak bases and strong acids cause depression of Δ \\ ̃ gm H . 3. Concentrations of weak bases capable of abolishing ΔpH, do not affect ATP synthesis. Concentrations of strong acids capable of abolishing Δψ affect only slightly ATP synthesis. Concentrations of weak bases and strong acids capable of causing a decline of ΔpH + Δψ inhibit ATP synthesis. 4. Depression of Δ \\ ̃ gm H is paralleled by inhibition of ATP synthesis and decline of ΔGp, the phosphate potential. Abolition of ATP synthesis occurs only when Δ \\ ̃ gm H is below 20 mV. The ΔG p/Δ \\ ̃ gm H ratio increases hyperbolically with the decrease of Δ \\ ̃ gm H .