Regulation of oxidative phosphorylation at the inner membrane of rat livermitochondria by calcium ions

The effect of accumulation of Ca2+ at physiological concentrations (10(-8)- 10(-6) M) on the rates of ATP synthesis and hydrolysis in rat liver mitocho ndria was studied. An addition of 5.10(-7) M Ca2+ resulted in the maximal r ates of synthesis and hydrolysis of ATP. Decrease in the concentration of C a2+ to 10(-8) M or its increase to 5.10(-6) M inhibited oxidative phosphory lation and ATP hydrolysis. It was found that the rate of oxidative phosphor ylation correlated with the phosphorylation level of a 3.5-kD peptide in th e mitochondrial inner membrane on varying the Ca2+ concentration. The possi ble regulation of oxidative phosphorylation in mitochondria by Ca2+ is disc ussed.