The Ca²⁺-Transport System of Yeast (Endomyces magnusii) Mitochondria: Independent Pathways for Ca²⁺ Uptake and Release

Y. I. Deryabina^* and R. A. Zvyagilskaya

Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky pr. 33, Moscow, 117071 Russia; fax: (095) 954-2732; E-mail: inbio@online.ru

^* To whom correspondence should be addressed. Y. I. Deryabina was awarded the Prize for Young Scientists for the year 2000 by the Russian Biochemical Society.

Received July 6, 2000

---

Some features of the Ca²⁺-transport system in mitochondria of the yeast Endomyces magnusii are considered. The Ca²⁺ uniporter was shown to be specifically activated by low concentrations of physiological modulators such as ADP, 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 preloaded E. magnusii yeast mitochondria is mediated by a Na⁺-independent pathway, 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.

---

KEY WORDS: yeast, Endomyces magnusii, mitochondria, calcium transport, regulation, ADP, NADH, calcium ions, Na⁺-independent calcium release

---