Onishi Hirofumi, Mochizuki Naoki, Morales Manuel F
Department of Structural Analysis, National Cardiovascular Center Research Institute, Fujishiro-dai, Suita, Osaka 565-8565, Japan.
Biochemistry. 2004 Apr 6;43(13):3757-63. doi: 10.1021/bi040002m.
Myosin is an ATP-hydrolyzing motor that is critical in muscle contraction. It is well established that in the hydrolysis that it catalyzes a water molecule attacks the gamma-phosphate of an ATP bound to its active site, but the details of these events have remained obscure. This is mainly because crystallographic search has not located an obvious catalytic base near the vulnerable phosphate. Here we suggest a means whereby this dilemma is probably overcome. It has been shown [Fisher, A. J., et al. (1995) Biochemistry 34, 8960-8972; Smith, C. A., and Rayment, I. (1996) Biochemistry 35, 5404-5417] that in an early event, Arg-247 and Glu-470 come together into a "salt-bridge". We suggest that in doing so they also position and orient two contiguous water molecules; one of these becomes the lytic water, perfectly poised to attack the bound gamma-phosphorus. Its hydroxyl moiety attacks the phosphorus, and the resulting proton transfers to the second water, converting it into a hydronium ion (as is experimentally observed). It is shown in this article how these central events of the catalysis are consistent with the behavior of several residues of the neighboring region.
肌球蛋白是一种水解ATP的马达蛋白，在肌肉收缩中起关键作用。人们已经清楚地知道，在它催化的水解反应中，一个水分子攻击与其活性位点结合的ATP的γ-磷酸基团，但这些事件的细节仍不清楚。这主要是因为晶体学研究在易受攻击的磷酸基团附近没有找到明显的催化碱基。在此我们提出一种可能克服这一困境的方法。研究表明[费舍尔，A. J.等人（1995年）《生物化学》34卷，8960 - 8972页；史密斯，C. A.和雷门特，I.（1996年）《生物化学》35卷，5404 - 5417页]，在早期事件中，精氨酸-247和谷氨酸-470会形成一个“盐桥”。我们认为，它们这样做时还会定位并排列两个相邻的水分子；其中一个水分子成为裂解水，完美地准备好攻击结合的γ-磷原子。其羟基部分攻击磷原子，产生的质子转移到第二个水分子上，将其转化为水合氢离子（正如实验所观察到的）。本文展示了这些催化核心事件如何与相邻区域几个残基的行为相一致。
