Davis J S
Biochem J. 1981 Aug 1;197(2):309-14. doi: 10.1042/bj1970309.
The self-assembly of myosin monomer into thick filament occurs via a two-step mechanism. At first a pair of myosin monomers reacts to form a parallel dimer; the dimer in turn adds to the filament ends at a rate that is independent of filament length. The rate of the dissociation reaction on the other hand is length-dependent. The 'off' rate constant has been shown to increase exponentially by a factor of 500 as the filament grows from the bare-zone out to its full length. The length of the filament is thus kinetically controlled; myosin is added to the filament at a fixed rate, whereas the dissociation rate increases to a point where equilibrium is established and the filament ceases to grow. The structural implications implicit in the mechanism are discussed.
肌球蛋白单体自组装成粗肌丝通过两步机制发生。首先,一对肌球蛋白单体反应形成平行二聚体;然后二聚体以与丝长度无关的速率添加到丝的末端。另一方面,解离反应的速率与长度有关。当丝从裸区生长到其全长时,“解离”速率常数已显示呈指数增加500倍。因此,丝的长度受动力学控制;肌球蛋白以固定速率添加到丝上,而解离速率增加到建立平衡且丝停止生长的程度。讨论了该机制中隐含的结构意义。