Interaction of cytochrome c with cytochrome c oxidase: an understanding of the high- to low-affinity transition.
Interaction of cytochrome c with cytochrome c oxidase: an understanding of the high- to low-affinity transition.
复制标题
细胞色素 c 与细胞色素 c 氧化酶的相互作用：了解高亲和力到低亲和力的转变。
DOI：
10.1016/0005-2728(90)90032-y
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Margoliash,E
中科院分区：
文献类型：
--
作者：
Garber,EA;Margoliash,E
本文研究了不同细胞色素和细胞色素氧化酶（ferrocytochromec：oxygen oxidoreductase，EC 1.9.3.1）制剂之间高亲和力和低亲和力电子转移反应的稳态动力学。马细胞色素c的第一和第二分子（I= 15 mM）结合的解离常数分别为5 · 10− 8 M和1 · 10− 5 M，接近于生物计量学Km值，并与细胞色素c和细胞色素氧化酶之间相互作用的受控结合模型一致（Speck，S.H.，Dye，D. Margoliash，E.（1984）Proc. Natl. Acad. Sci. USA 81，346-351），其假定细胞色素的第二分子的结合减弱了第一分子的结合，导致低亲和力动力学。虽然极谱法测定的高亲和力反应的Km值与电化学法观察到的Km值相当，但低亲和力Km值要小一个数量级，不能归因于细胞色素c的第二个分子的结合。增加粘度对极谱法测定的低亲和反应的Vmax无影响，但使Km增大。因此，从高亲和力到低亲和力动力学的转变取决于生产性碰撞的频率，正如预期的滞后模型归因于转换的引发状态的氧化酶的捕获营业额。在离子强度高于150 mM时，细胞色素氧化的速率降低，与细胞色素的净电荷计算值无任何相关性，表明两种蛋白质彼此接近的限速重排。
The steady-state kinetics of high- and low-affinity electron transfer reactions between various cytochromescand cytochromecoxidase (ferrocytochromec:oxygen oxidoreductase, EC 1.9.3.1) preparations were studied spectrophotometrically and polarographically. The dissociation constants for the binding of the first and second molecules of horse cytochromec(I= 15 mM) are 5 · 10−8M and 1 · 10−5M, respectively, close to the spectrophotometricKmvalues and consistent with the controlled binding model for the interaction between cytochromecand cytochrome oxidase (Speck, S.H., Dye, D. and Margoliash, E. (1984) Proc. Natl. Acad. Sci. USA 81, 346–351) which postulates that the binding of a second molecule of cytochromecweakens that of the first, resulting in low-affinity kinetics. While theKmof the polarographically assayed high-affinity reaction is comparable to that observed spectrophotometrically, the low-affinityKmis over an order of magnitude smaller and cannot be attributed to the binding of a second molecule of cytochromec. Increasing the viscosity has no effect on theVmaxof the low-affinity reaction assayed polarographically, but increases theKm. Thus, the transition from high- to low-affinity kinetics is dependent on the frequency of productive collisions, as expected for a hysteresis model ascribing the transition to the trapping of the oxidase in a primed state for turnover. At ionic strengths above 150 mM, the rate of cytochromecoxidation decreases without any correlation to the calculated net charge of the cytochromec, indicating rate-limiting rearrangement of the two proteins in proximity to each other.