CHARACTERIZATION OF A HIGH-CAPACITY CALCIUM-TRANSPORT SYSTEM IN MITOCHONDRIA OF THE YEAST ENDOMYCES-AGNUSII

The Ca2+ transport system of Endomyces magnusii mitochondria has been shown previously to be activated by spermine. Here we report it tea be regulated also by low, physiological ADP concentrations, by the intra mitochondrial NADH/NAD(+) ratio, and by Ca2+ ions. The combination of all these physiological modulators induced high initial rates of Ca2uptake and high Ca2+-buffering capacity of yeast mitochondria, enablin g them to lower the medium [Ca2+] to similar to 0.2 mu M. The mechanis ms of stimulation by these agents are discussed.