Shol'ts K F, Mamaev D V
Biokhimiia. 1985 Nov;50(11):1877-83.
Interaction of cytochrome c with electron carriers in intact and damaged (with destroyed outer membrane) rat liver mitochondria was studied. It was shown that the increase in ionic strength causes changes in the respiration rate of damaged mitochondria due to the reduction of the cytochrome c affinity for its binding sites in the organelles. This suggests that cytochrome c concentration in the intermembrane space of intact mitochondria is increased by salts, whereas the increase in ionic strength has a slight influence on the rates of succinate oxidase and external rotenone-insensitive NADH-oxidase of intact mitochondria. At low ionic strength values, the Michaelis constant (KM) value of external NADH-oxidase for cytochrome c exceeds by one order of magnitude that for succinate oxidase, while the maximal activity of these two systems is nearly the same. The increase in ionic strength causes an increase in the KM value for both oxidases. Interaction of cytochrome c with mitochondrial proteins was modelled by cytochrome c interaction with cibacron-dextran anions. It was concluded that the ionic strength-sensitive electrostatic interactions play a decisive role in cytochrome c binding to electron carriers in mitochondrial membranes. However, cytochrome c content and its binding parameters in intact-mitochondrial membranes prevent the latent activity of external NADH oxidase to be revealed in intact mitochondria after the increase in the ionic strength of the surrounding medium.
研究了细胞色素c与完整及受损（外膜被破坏）大鼠肝线粒体中电子载体的相互作用。结果表明，离子强度的增加会导致受损线粒体呼吸速率发生变化，这是由于细胞色素c对细胞器中其结合位点的亲和力降低所致。这表明完整线粒体膜间隙中的细胞色素c浓度会因盐类而增加，而离子强度的增加对完整线粒体的琥珀酸氧化酶和外源性鱼藤酮不敏感的NADH氧化酶的速率影响较小。在低离子强度值时，外源性NADH氧化酶对细胞色素c的米氏常数（KM）值比对琥珀酸氧化酶的KM值高出一个数量级，而这两个系统的最大活性几乎相同。离子强度的增加会导致两种氧化酶的KM值均升高。通过细胞色素c与汽巴克隆-葡聚糖阴离子的相互作用对细胞色素c与线粒体蛋白的相互作用进行了模拟。得出的结论是，对离子强度敏感的静电相互作用在细胞色素c与线粒体膜中电子载体的结合中起决定性作用。然而，完整线粒体膜中的细胞色素c含量及其结合参数阻止了在周围介质离子强度增加后完整线粒体中外源性NADH氧化酶的潜在活性得以显现。
