The Ca2+-transport system of yeast (Endomyces magnusii) mitochondria: Independent pathways for Ca2+ uptake and release

Some features of the Ca2+-transport system in mitochondria of the yeast End omyces magnusii are considered. The Ca2+ uniporter was shown to be specific ally activated by low concentrations of physiological modulators such as AD P, NADH, spermine, and Ca2+ itself. The Na+-independent system responsible for Ca2+ release from Ca2+-preloaded yeast mitochondria was characterized. The rate of the Ca2+ release was proportional to the Ca2+ load, insensitive to cyclosporin A and to Na+, inhibited by La3+, TPP+, P-i, and nigericin, while being activated by spermine. We conclude that Ca2+ release from prelo aded E. magnusii yeast mitochondria is mediated by a Na+-independent pathwa y, very similar to that in mitochondria from nonexcitable mammalian tissues . A scheme describing an arrangement of the Ca2+ transport system of yeast mitochondria is proposed.