Evidence for energy-dependent change in phosphate binding for mitochondrial oxidative phosphorylation based on measurements of medium and intermediate phosphate-water exchanges.
Evidence for energy-dependent change in phosphate binding for mitochondrial oxidative phosphorylation based on measurements of medium and intermediate phosphate-water exchanges.
复制标题
基于中等和中等磷酸盐-水交换的测量，线粒体氧化磷酸化的磷酸盐结合的能量依赖性变化的证据。
DOI：
10.1016/s0021-9258(17)40483-2
复制
发表时间：
1977
期刊：
影响因子：
--
通讯作者：
P. Boyer
中科院分区：
文献类型：
--
作者：
J. Rosing;C. Kayalar;P. Boyer
牛心亚软骨颗粒催化的交换反应的特征为氧化磷酸化的能量转换步骤提供了新的见解。在 ATP、ADP 和 Pi 存在下，平衡 HOH 交换中总 Pi 的解偶联剂不敏感部分是平衡 HOH 交换中的中间 Pi，即在 Pi 从催化位点释放之前通过 ATP 水解形成的 Pi 发生的交换。介质 Pi 与 HOH 的交换对解偶联剂的敏感度与平衡 ATP 交换和净氧化磷酸化中的 Pi 一样敏感，这表明需要解偶联剂敏感的通电状态（可能是跨膜电位或质子梯度）才能使介质 Pi 达到反应状态。催化位点（平衡 ATP + HOH 中的 ADP + Pi）的共价键形成和断裂步骤似乎对解偶联剂相对不敏感。因此，就解偶联剂耗散跨膜质子动力而言，这种力不太可能通过 Pi 氧的直接质子化来驱动 ATP 形成。当仅添加 Pi 和 ADP，并且充分阻断腺苷酸激酶从添加的 ADP 形成 ATP 以及随后的 ATP 水解时，在平衡 HOH 交换中观察不到 Pi，这证明了这种交换需要通过 ATP 结合和裂解来供能。这种解偶联剂不敏感的赋能被认为代表了一种构象赋能状态，可以可逆地用于产生伴随 ADP 和 Pi 释放的跨膜质子动力。通过改进的程序估计的各种交换速率与催化位点处 ATP 水解动态逆转发生的所有氧交换兼容。
Characteristics of the exchange reactions catalyzed by beef heart submitochondrial particles give new insight into energy transducing steps of oxidative phosphorylation. The uncoupler-insensitive portion of the total Pi in equilibrium HOH exchange in presence of ATP, ADP, and Pi is the intermediate Pi in equilibrium HOH exchange, that is the exchange occurring with Pi formed by hydrolysis of ATP prior to release of Pi from the catalytic site. The exchange of medium Pi with HOH is as sensitive to uncouplers as the Pi in equilibrium ATP exchange and net oxidative phosphorylation, demonstrating a requirement of an uncoupler-sensitive energized state, probably a transmembrane potential or proton gradient, for bringing medium Pi to the reactive state. The covalent bond forming and breaking step at the catalytic site (ADP + Pi in equilibrium ATP + HOH) appears relatively insensitive to uncouplers. Thus to the extent that uncouplers dissipate transmembrane proton-motive force, it is unlikely that such a force is used to drive ATP formation by direct protonations of Pi oxygens. When only Pi and ADP are added and formation of ATP from added ADP by adenylate kinase and subsequent ATP hydrolysis are adequately blocked, no Pi in equilibrium HOH exchange can be observed, demonstrating a requirement of energization by ATP binding and cleavage for such an exchange. This uncoupler-insensitive energization is suggested to represent a conformationally energized state that can be used reversibly to develop a transmembrane protonmotive force accompanying ADP and Pi release. Rates of various exchanges as estimated by improved procedures are compatible with all oxygen exchanges occurring by dynamic reversal of ATP hydrolysis at the catalytic site.