Slow Ca2+‐induced inactive/active transition of the energy‐dependent Ca2+ transporting system of rat liver mitochondria: clue for Ca2+ influx cooperativity

FEBS Letters

Vinogradov, A.D.¹  Kasparinsky, F.O.¹ 

[1] Department of Biochemistry, School of Biology, Moscow State University, 119899 Moscow, Russian Federation

关键词: Ca2+ transport;    Cooperative kinetics;    Rat liver mitochondria;    EGTA;    [ethylenebis(oxyethylenenitrilo)]tetraacetic acid;    FCCP;    carbonylcyanide-4-trifluoremethoxyphenylhydrazone;    HEPES;    N-2-hydroxyethylpiperazine-N′-ethanesulfonic acid;   

DOI  :  10.1016/0014-5793(96)00606-0

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Rat liver mitochondria essentially free of endogenous Ca²⁺ show low initial rate of energy-dependent Ca²⁺ uptake. Preincubation of mitochondria under de-energized conditions in the presence of small amounts of external Ca²⁺ results in a 8–10-fold time-dependent increase of energy-dependent Ca²⁺ uptake. Ca²⁺-dependent activation of the Ca²⁺-transporting system follows first-order kinetics ( in the presence of 5 μM Ca²⁺ at 20°C). Ca²⁺-activated mitochondria demonstrate a simple hyperbolic initial rate-Ca²⁺ concentration dependence, whereas strong apparent cooperativity is observed in the velocity-substrate curves for Ca²⁺-depleted mitochondria. It is concluded that apparent cooperativity of the energy-dependent Ca²⁺ uptake is due to slow (as compared with the ‘turnover number’) activation of a Ca²⁺-specific uniporter which is inactive in the absence of external Ca²⁺.

【 授权许可】

Unknown