Characterization of a high capacity calcium transport system in mitochondria of the yeast Endomyces magnusii

The Ca2+ transport system of Endomyces magnusii mitochondria has been shown previously to be activated by spermine. Here we report it to be regulated also by low, physiological ADP concentrations, by the intramitochondrial NADH/NAD+ ratio, and by Ca2+ ions. The combination of all these physiological modulators induced high initial rates of Ca2+ uptake and high Ca2+-buffering capacity of yeast mitochondria, enabling them to lower the medium [Ca2+] to approximately 0.2 microM. The mechanisms of stimulation by these agents are discussed.