A kinetic study of salt-induced denaturation of actin during storage at low temperature

少量的F-肌球蛋白复合体在加热时作为游离肌球蛋白分子的交联剂，被认为是肌动蛋白诱导改善肌球蛋白凝胶形成能力的先决条件。因此，肌球蛋白热诱导凝胶的性质取决于肌动蛋白在盐处理过程中的稳定性。本工作旨在阐明盐诱导的肌动蛋白在低温孵育过程中变性的机制。通过测定肌动蛋白的脱氧核糖核酸酶L抑制能力的动力学分析表明，当肌动蛋白溶液在低温(0ﾟC)下孵育时，肌动蛋白的变性遵循不可逆的连续反应理论(F-adp-肌动蛋白--&gt；G-adp-肌动蛋白-&gt；变性肌动蛋白)。在F-肌动蛋白溶液中加入足够量的ATP可以有效地延缓肌动蛋白变性的进程。ATP被认为可以稳定盐处理过程中解聚的G-肌动蛋白的结构。也就是说，ATP的存在延缓了G-ADP-肌动蛋白--&gt；变性肌动蛋白的过程。很明显，在0ﾟC孵育过程中，少量的HMM加速了F-肌动蛋白的解聚速度。因此，释放的G-肌动蛋白可能在没有ATP的情况下迅速进入变性过程。在含有肌动蛋白或肌动蛋白-HMM复合体的溶液中加入原肌球蛋白，在0.2MKCI和0.6MKCI之间，肌动蛋白的变性受到显著抑制。从这一结果可以看出，当离子强度低于0.6MKCI时，原肌球蛋白稳定肌动蛋白细丝不解体

The small amount of F-actomyosin complex acts as a cross-linker with the free myosin molecule on heating, and it is considered to be a prerequisite for actin-induced improvement in the gel formability of myosin. Therefore, the property of heat-induced gel of myosin depends on the stability of actin during treatment with salt. The present work was conducted to elucidate the mechanism of salt-induced denaturation of actin during incubation at a low temperature.1. A kinetic analysis by measuring DNase l inhibition capacity of actin demonstrated that the denaturation of actin obeys the theory of an irreversible continuous reaction (F-ADP-actin ---> G-ADP-actin ---> denatured actin) when actin solution is incubated at a low temperature (0ﾟC).2. The addition of a sufficient amount of ATP to an F-actin solution effectively retards the progress of the denaturation of actin. ATP is thought to stabilize the structure of G-actin depolymerized during treatment with salt. That is, the present of ATP retards the process of G-ADP-actin -->denatured actin.3. It has become apparent that a small amount of HMM accelerates the rate of depolymerization of F-actin during incubation at 0ﾟC.As a result, released G-actin is presumed to enter quickly the denaturation process without ATP.4. When tropomyosin was added to solution containing actin alone or actin-HMM complex, the denaturation of actin was suppressed remarkably between 0.2 M KCI and 0.6 M KCI.From this result, it is clear that tropomyosin stabilizes the actin filament against disassembly at ionic strengths lower than 0.6 M.KCI