Impact of profilin on actin-bound nucleotide exchange and actin polymerization dynamics
Impact of profilin on actin-bound nucleotide exchange and actin polymerization dynamics
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DOI：
10.1021/bi981543c
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发表时间：
1999-03-02
期刊：
影响因子：
2.9
通讯作者：
Gershman, LC
中科院分区：
文献类型：
--
作者：
Selden, LA;Kinosian, HJ;Gershman, LC
我们研究了profilin对核苷酸结合肌动蛋白和稳态肌动蛋白聚合的影响。在生理条件下，ATP和ADP从单体Mg-肌动蛋白上解离的速率常数分别为0.003和0.009 s（-1）。Profilin使MgATP-肌动蛋白的解离速率常数增加到0.08 s（-1），MgADP-肌动蛋白的解离速率常数增加到1.4 s（-1）。因此，profilin可以增加肌动蛋白结合ADP的ATP交换率140倍。发现profilin对单体肌动蛋白的亲和力与MgATP-肌动蛋白和MgADP-肌动蛋白相似。使用连续超声处理以允许研究具有持续高长丝末端浓度的溶液。在稳态超声处理期间，F-肌动蛋白朝向ADP-肌动蛋白的临界浓度解聚[Pantaloni，D.，等人（1984）J.Biol.Chem.259，6274-6283]，我们的分析表明，在这些条件下，大量的细丝含有末端ADP-肌动蛋白亚基。向该系统中加入profilin增加了聚合物浓度，并增加了超声处理期间的稳态ATP酶活性。这些数据被解释为快速交换ATP ADP的profilin-ADP-肌动蛋白复合物，导致快速ATP-肌动蛋白再生。profilin的一个重要功能可能是在单体循环速率超过单体肌动蛋白的固有核苷酸交换速率期间为细丝的生长末端提供ATP-肌动蛋白。
We have investigated the effects of profilin on nucleotide binding to actin and on steady state actin polymerization. The rate constants for the dissociation of ATP and ADP from monomeric Mg-actin at physiological conditions are 0.003 and 0.009 s(-1), respectively. Profilin increases these dissociation rate constants to 0.08 s(-1) for MgATP-actin and 1.4 s(-1) for MgADP-actin. Thus, profilin can increase the rate of-exchange of actin-bound ADP for ATP by 140-fold. The affinity of profilin for monomeric actin is found to be similar for MgATP-actin and MgADP-actin. Continuous sonication was used to allow study of solutions having sustained high filament end concentrations. During sonication at steady state, F-actin depolymerizes toward the critical concentration of ADP-actin [Pantaloni, D., et al. (1984) J. Biol. Chem. 259, 6274-6283], our analysis indicates that under these conditions a significant number of filaments contain terminal ADP-actin subunits. Addition of profilin to this system increases the polymer concentration and increases the steady state ATPase activity during sonication. These data are explained by the fast exchange of ATP for ADP on the profilin-ADP-actin complex, resulting in rapid ATP-actin regeneration. An important function of profilin may be to provide the growing ends of filaments with ATP-actin during periods when the monomer cycling rate exceeds the intrinsic nucleotide exchange rate of monomeric actin.