Calcium exerts an indirect effect on ATP-dependent proteolysis of rat liver mitochondria

The ATP-dependent proteolysis of rat liver mitochondria prepared in electrolyte-poor sucrose media requires the presence of Ca2+. Lanthanum, an inhibitor of Ca2+ uptake, inhibits the proteolysis. In contrast, proteolysis of mitochondria prepared in a salt medium does not require Ca2+, nor is it inhibited by lanthanum. It is concluded that Caa+ exerts its effect in an indirect manner, by causing swelling and thereby increasing the accessibility of the membrane proteins of the inner mitochondrial membrane.