Carlier M F, Didry D, Erk I, Lepault J, Pantaloni D
Laboratoire d'Enzymologie, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
J Biol Chem. 1994 Feb 4;269(5):3829-37.
Myosin subfragment-1-induced polymerization of G-actin into arrowhead-decorated F-actin-myosin subfragment-1 (S1) filaments has been studied at low ionic strength and in the absence of ATP, using a combination of light scattering, fluorescence of 4-nitrobenz-2-oxa-1,3-diazol-7-yl- or pyrenyl-labeled actin, sedimentation, and electron microscopy techniques. When G-actin is in excess over myosin subfragment-1, the initial formation of fully decorated F-actin-S1 filaments, in which the actin:S1 molar ratio is 1:1, is followed by further incorporation of G-actin subunits in the polymer concomitant with the redistribution of the myosin heads along the polymer, leading to partially decorated filaments containing less than one S1/actin, in equilibrium with G-actin. This process leads to an overshoot in the light-scattering polymerization curves at high actin:S1 ratios. The concentration of G-actin at equilibrium with partially decorated filaments is a nonlinear function of the molar fraction of S1 in the polymer, indicating that actin-actin-S1 interactions are energetically more favorable than actin-actin or actin-S1-actin-S1 interactions.
在低离子强度且无ATP的条件下，结合使用光散射、4-硝基苯-2-恶唑-1,3-二氮杂萘-7-基或芘基标记的肌动蛋白荧光、沉降和电子显微镜技术，研究了肌球蛋白亚片段-1诱导G-肌动蛋白聚合成箭头状装饰的F-肌动蛋白-肌球蛋白亚片段-1（S1）丝的过程。当G-肌动蛋白相对于肌球蛋白亚片段-1过量时，首先形成完全装饰的F-肌动蛋白-S1丝（其中肌动蛋白与S1的摩尔比为1:1），随后G-肌动蛋白亚基进一步掺入聚合物中，同时肌球蛋白头部沿聚合物重新分布，导致形成部分装饰的丝，其中每个肌动蛋白含有的S1少于一个，与G-肌动蛋白处于平衡状态。在高肌动蛋白与S1比例时，该过程导致光散射聚合曲线出现过冲现象。与部分装饰的丝处于平衡状态的G-肌动蛋白浓度是聚合物中S1摩尔分数的非线性函数，这表明肌动蛋白-肌动蛋白-S1相互作用在能量上比肌动蛋白-肌动蛋白或肌动蛋白-S1-肌动蛋白-S1相互作用更有利。
