Biochemical kinetics of porcine cardiac subfragment-1.
Biochemical kinetics of porcine cardiac subfragment-1.
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猪心脏亚片段-1的生化动力学。
DOI：
10.1161/01.res.60.1.39
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发表时间：
1987
影响因子：
20.1
通讯作者：
White,MP
中科院分区：
文献类型：
--
作者：
Stein,LA;White,MP
心肌肌球蛋白亚片段-1的肌动蛋白结合和atp酶动力学与先前对骨骼肌球蛋白亚片段的研究进行了比较。对兔骨骼亚片段-1 （S-1）的动力学研究揭示了肌动球蛋白atp酶活性的两个重要特征。首先，当S-1与肌动蛋白结合和与肌动蛋白分离时，肌球蛋白亚片段-1水解ATP。其次，达到最大ATP酶活性的一半所需的肌动蛋白浓度Ka（ATP酶）远远低于在ATP稳态水解过程中结合一半亚片段-1所需的肌动蛋白浓度Ka（结合）。这些动力学事实要求骨骼肌球蛋白水解ATP而不与肌动蛋白分离；因此，存在ATP水解的“非解离”途径。本文报道的研究表明，猪心脏S-1与兔骨骼S-1非常相似。在与先前对骨骼S-1的研究相同的条件下，猪心脏S-1的Ka（atp酶）与骨骼S-1的报道大致相等。Ka（绑定）也是如此。对Ka（ATPase）和Ka（结合）的比较表明，对于心脏蛋白来说，Ka（ATPase）比Ka（结合）强4到6倍，也就是说，在达到50%结合所需的肌动蛋白的五分之一时，达到了一半的最大atp酶活性。外推的最大atp酶活性在饱和肌动蛋白浓度下，心脏S-1始终比骨骼S-1慢约2.5倍。此外，对高肌动蛋白浓度和交联的actoS-1 ATP酶活性的研究显示，actoS-1没有明显的抑制作用，这意味着心肌肌球蛋白亚片段-1水解ATP需要“非解离”途径。
The actin binding and ATPase kinetics of cardiac myosin subfragment-1 were compared with prior studies on skeletal myosin subfragments. Previous kinetic studies on rabbit skeletal subfragment-1 (S-1) have revealed two important features of the actomyosin ATPase activity. First, hydrolysis of ATP by myosin subfragment-1 proceeds both when S-1 is bound to actin and when it is dissociated from actin. Second, the actin concentration required to reach half the maximum ATPase activity, Ka(ATPase), is considerably lower than the actin concentration required to bind half the subfragment-1 during steady state hydrolysis of ATP, Ka(binding). These kinetic facts require that skeletal myosin hydrolyze ATP without dissociating from actin; therefore, a "nondissociating" pathway for ATP hydrolysis exists. The studies reported here show that porcine cardiac S-1 is very similar to rabbit skeletal S-1. Under identical conditions to prior work on skeletal S-1, the Ka(ATPase) of porcine cardiac S-1 is approximately equal to that reported for skeletal S-1. This is also true for Ka(binding). Comparison of Ka(ATPase) and Ka(binding) shows that for cardiac proteins Ka(ATPase) is fourfold to sixfold stronger than Ka(binding), i.e., half maximal ATPase activity is achieved at about one fifth the actin necessary to reach 50% binding. The extrapolated maximum ATPase activity at saturating actin concentration for cardiac S-1 is consistently slower than skeletal S-1 by about a factor of 2.5. Furthermore, studies of the actoS-1 ATPase activity at high actin concentrations as well as with crosslinked actoS-1 show no significant inhibition, implying the requirement of a "nondissociating" pathway for ATP hydrolysis by cardiac myosin subfragment-1.