EFFECT OF VILLIN ON THE KINETICS OF ACTIN POLYMERIZATION
EFFECT OF VILLIN ON THE KINETICS OF ACTIN POLYMERIZATION
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DOI：
10.1021/bi00307a012
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发表时间：
1984-01-01
期刊：
影响因子：
2.9
通讯作者：
MOOSEKER, MS
中科院分区：
文献类型：
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作者：
WALSH, TP;WEBER, A;MOOSEKER, MS
测定了绒毛蛋白对肌动蛋白临界浓度及其聚合动力学的影响。在维林和10微米钙的存在下，肌动蛋白的临界浓度从0.2微米增加到0.9微米。维林对临界浓度的影响是因为它有能力阻断肌动蛋白细丝的带刺末端，即两端具有不同单体结合常数的聚合物的高亲和力末端。因此，当绒毛蛋白与肌动蛋白的比例约为1：1000时，可防止低于0.8微米的肌动蛋白聚合。此外，维林的作用是饱和的，即一旦达到最大变化，其临界浓度随浓度的增加而保持不变。此外，肌动蛋白细丝的断裂会导致单体浓度的快速、瞬时下降。随着无帽细丝的消失，肌动蛋白单体浓度恢复到碎裂前的水平。计算得到肌动蛋白细丝带刺末端的结合常数大于1011M-1。测定了肌动蛋白细丝两端的伸长和解聚速率常数。在导致完全解聚的条件下，从带刺末端开始的解聚速率常数大约是稳态条件下的10倍。对这一发现的可能解释及其对可能的调控机制的影响进行了讨论。
The effect of villin on the critical concentration of actin and on the kinetics of its polymerization was measured. In the presence of villin and 10 .mu.M Ca, the critical concentrations of actin increased from 0.2 to 0.9 .mu.M. This effect of villin on the critical concentration was the result of its well-documented ability to block the barbed end of actin filaments, i.e., the high-affinity end of a polymer with a different monomer binding constant at each end. Thus, below 0.8 .mu.M actin polymerization was prevented when the ratio of villin to actin was about 1 in 1000. Furthermore, the effect of villin was saturable, i.e., the critical concentration remained constant with increasing with concentration once the maximal change had been obtained. In addition, fragmentation of actin filaments previously capped with villin, producing uncapped filaments, caused a rapid, transient fall of the monomer concentration. With the disappearance of the uncapped filaments the actin monomer concentration returned to that measured before fragmentation. The binding constant of villin to the barbed end of the actin filament was calculated to be greater than 1011 M-1. The rate constants of elongation and of depolymerization at each end of an actin filament were measured. The depolymerization rate constant from the barbed end was about 10 times greater under conditions leading to complete depolymerization than under steady-state conditions. A possible explanation for the finding and its implication for possible regulatory mechanisms are discussed.