Effect of potassium and valinomycin on oxidative phosphorylation in intact beef heart mitochondria and submitochondrial particles

Abstract

Beef heart mitochondria and submitochondrial particles have been used to measure parameters of oxidative phosphorylation with respect to varying concentrations of potassium and valinomycin. In the absence of valinomycin, intact mitochondria showed little response to potassium. The presence of valinomycin caused the following response of intact mitochondria to increasing potassium concentrations: lower ADP/O ratio, lower rate of phosphorylation, no increase in state-3 respiration, higher respiration rate in state 4, and lower respiratory control. In contrast, the P/O ratio of submitochondrial particles was not altered significantly by increasing potassium concentrations in either the absence or the presence of valinomycin. It is suggested that potassium does not interact directly with the oxidative phosphorylation system but may compete with ATP synthesis in intact beef heart mitochondria via an energyrequiring potassium transport system.