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首页> 外文期刊>Biochemistry >Mechanism of myosin subfragment-1-induced assembly of CaG-actin and MgG-actin into F-actin-S1-decorated filaments
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Mechanism of myosin subfragment-1-induced assembly of CaG-actin and MgG-actin into F-actin-S1-decorated filaments

机译：肌球蛋白亚片段1诱导CaG-肌动蛋白和MgG-肌动蛋白组装成F-肌动蛋白-S1装饰丝的机制

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The kinetics and mechanism of myosin subfragment-1-induced polymerization of G-actin into F-actin-S1-decorated filaments have been investigated in low ionic strength buffer and in the absence of free ATP. The mechanism of assembly of F-actin-S1 differs from salt-induced assembly of F-actin. Initial condensation of G-actin and S1 into oligomers in reversible equilibrium is a prerequisite step in the formation of F-actin-S1 . Oligomers have a relatively low stability (10(6) M-1) and contain S1 in a molar ratio to actin close to 0.5. Increased binding of S1 up to a 1:1 molar ratio to actin is associated with further irreversible condensation of oligomers into large F-actin-S1 structures of very high stability. In contrast to salt-induced assembly of F-actin, no monomer-polymer equilibrium, characterized by a critical concentration, can be defined for F-actin-S1 assembly, and end-to-end annealing of oligomers is predominant over growth from nuclei in the kinetics. Simultaneous recordings of the changes in light scattering, pyrenyl- and NBD-actin fluorescence, ATP hydrolysis, and release of Pi during the polymerization process have been analyzed to propose a minimum kinetic scheme for assembly, within which several elementary steps, following oligomer formation, are required for assembly of F-actin-S1. ATP hydrolysis occurs before polymerization of MgATP-G-actin but not of CaATP-G-actin. The release of inorganic phosphate occurs on F-actin-S1 at the same rate as on F-actin.
机译：在低离子强度缓冲液和没有游离ATP的条件下，研究了肌球蛋白亚片段1诱导的G-肌动蛋白聚合成F-肌动蛋白-S1装饰丝的动力学和机理。 F-肌动蛋白-S1的组装机制与盐诱导的F-肌动蛋白的组装不同。 G-肌动蛋白和S1在可逆平衡下初始缩合为低聚物是F-肌动蛋白-S1形成的前提步骤。低聚物具有相对较低的稳定性（10（6）M-1），并且含有的S1与肌动蛋白的摩尔比接近0.5。 S1与肌动蛋白的摩尔比增加至1：1的增加与低聚物进一步不可逆地缩合为稳定性非常高的大F-actin-S1结构有关。与盐诱导的F-肌动蛋白组装不同，F-肌动蛋白-S1组装不能定义以临界浓度为特征的单体-聚合物平衡，并且低聚物的端到端退火主要是从核的生长在动力学上。分析了同时记录聚合过程中光散射，pyr基和NBD-肌动蛋白的荧光，ATP水解和Pi释放的变化，以提出组装的最小动力学方案，其中包括低聚物形成后的几个基本步骤， F-actin-S1的组装必需。 ATP水解发生在MgATP-G-肌动蛋白聚合之前，而不发生在CaATP-G-肌动蛋白聚合之前。无机磷酸盐的释放以与F-肌动蛋白相同的速率在F-肌动蛋白-S1上发生。

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