肌球蛋白分子两个头部的结构与功能。I. 三磷酸腺苷酶反应过程中二磷酸腺苷与肌原纤维的结合。

Structure and function of the two heads of the myosin molecule. I. Binding of adenosine diphosphate to myofibrils during the adenosinetriphosphatase reaction.

Arata T, Tonomura Y

J Biochem. 1976 Dec;80(6):1353-8. doi: 10.1093/oxfordjournals.jbchem.a131408.

Abstract

The myosin content of myofibrils was found to be 51% by SDS-gel electrophoresis. 2. The initial burst of Pi liberation of the ATPase [EC 3.6.1.3] of a solution of myofibrils in 1 M KCl was measured in 0.5 M KCl, and found to be 0.93 mole/mole of myosin. 3. The amount of ADP bound to myofibrils during the ATPase reaction and the ATPase activity were measured by coupling the myofibrillar ATPase reaction with sufficient amounts of pyruvate kinase [EC 2.7.1.40] and PEP to regenerate ATP. The maximum amount of ADP bound to myofibrils in 0.05M KCl and in the relaxed state was about 1.5 mole/mole of myosin. On the other hand, the ATPase activity exhibited substrate inhibition, and the amount of ATP required for a constant level of ATPase activity was smaller than that required for the maximum binding of ADP to myofibrils. 4. The maximum amount of ADP bound to myofibrils in 0.5 M KCl was about 1.9 mole/mole of myosin. When about one mole of ADP was found to 1 mole of myosin in myofibrils, the myofibrillar ATPase activity reached the saturated level, and with further increase in the concentration of ATP one more mole of ADP was found per mole of myosin.

摘要

通过十二烷基硫酸钠-凝胶电泳法发现肌原纤维的肌球蛋白含量为51%。2. 在0.5M氯化钾中测定了1M氯化钾中肌原纤维溶液的ATP酶[EC 3.6.1.3]最初释放无机磷酸的速率，发现为每摩尔肌球蛋白0.93摩尔。3. 通过将肌原纤维ATP酶反应与足量的丙酮酸激酶[EC 2.7.1.40]和磷酸烯醇丙酮酸偶联以再生ATP，来测量ATP酶反应过程中与肌原纤维结合的ADP量以及ATP酶活性。在0.05M氯化钾中且处于松弛状态时，与肌原纤维结合的ADP的最大量约为每摩尔肌球蛋白1.5摩尔。另一方面，ATP酶活性表现出底物抑制作用，维持恒定ATP酶活性所需的ATP量小于使ADP与肌原纤维最大结合所需的ATP量。4. 在0.5M氯化钾中，与肌原纤维结合的ADP的最大量约为每摩尔肌球蛋白1.9摩尔。当在肌原纤维中发现每摩尔肌球蛋白结合约1摩尔ADP时，肌原纤维ATP酶活性达到饱和水平，随着ATP浓度进一步增加，每摩尔肌球蛋白又发现结合1摩尔ADP。