Kouyama T, Mihashi K
Eur J Biochem. 1980 Apr;105(2):279-87. doi: 10.1111/j.1432-1033.1980.tb04499.x.
The single-photoelectron counting technique was used for measurement of the fluorescence decay kinetics of N-(1-pyrene)maleimide conjugated to the fast reactive cysteine of actin. The fluorescence decay curve of the labelled G-actin could not be described by a single-exponential function but by a double-exponential function. Polymerization of actin was accompanied by significant changes in the decay parameters of the two decay components. We found that the ionic strength, which plays an important role in the G-F equilibrium, scarcely affected these parameters provided that the labelled actin exists in the monomeric state. Thus it is suggested that the conformational change of actin protomer occurs at the time of association. When heavy meromyosin was added to the labelled F-actin, the decay parameter changed monotonically on increasing saturation of binding of heavy meromyosin and it levelled-off around a ratio of heavy meromyosin:actin of 0.5 mol/mol. Decay parameters under the influence of heavy meromyosin had values intermediate between those observed for the labelled G-actin and for the labelled F-actin. Therefore, it is suggested that binding of heavy meromyosin to F-actin alters the conformation of actin protomer towards that similar to G-actin.
单光电子计数技术用于测量与肌动蛋白快速反应性半胱氨酸结合的N-(1-芘)马来酰亚胺的荧光衰减动力学。标记的G-肌动蛋白的荧光衰减曲线不能用单指数函数描述，而要用双指数函数描述。肌动蛋白的聚合伴随着两个衰减成分的衰减参数的显著变化。我们发现，在G-F平衡中起重要作用的离子强度，只要标记的肌动蛋白以单体状态存在，就几乎不影响这些参数。因此，有人提出肌动蛋白原的构象变化发生在缔合时。当向标记的F-肌动蛋白中加入重酶解肌球蛋白时，随着重酶解肌球蛋白结合饱和度的增加，衰减参数单调变化，并在重酶解肌球蛋白与肌动蛋白的比例为0.5 mol/mol左右趋于平稳。在重酶解肌球蛋白影响下的衰减参数值介于标记的G-肌动蛋白和标记的F-肌动蛋白所观察到的值之间。因此，有人提出重酶解肌球蛋白与F-肌动蛋白的结合会使肌动蛋白原的构象向类似于G-肌动蛋白的方向改变。
