Interaction of thymosin beta 4 with muscle and platelet actin: implications for actin sequestration in resting platelets.
Interaction of thymosin beta 4 with muscle and platelet actin: implications for actin sequestration in resting platelets.
复制标题
胸腺素β4与肌肉和血小板肌动蛋白的相互作用：对静息血小板中肌动蛋白隔离的影响。
DOI：
10.1021/bi00142a002
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发表时间：
1992
期刊：
影响因子：
2.9
通讯作者：
Safer,D
中科院分区：
文献类型：
--
作者：
Weber,A;Nachmias,VT;Pennise,CR;Pring,M;Safer,D
修订稿于 1992 年 4 月 21 日收到摘要：Tj84 与肌肉肌动蛋白相互作用的定量测量表明，其唯一的生理作用是单体隔离。 T/34在生理盐条件下与单体肌动蛋白形成1:1复合物。肌动蛋白的 K¿ 不受钙的影响。 T¡ 84 仅与肌动蛋白单体结合，不与细丝末端或细丝旁边结合。吨/？ 4-肌动蛋白复合物不会在有刺或尖端处延长肌动蛋白丝，并且与肌动蛋白结合蛋白不同，T/S4 不会特异性抑制聚合成核。我们评估了静息血小板中可被 ß4 隔离的单体肌动蛋白的比例。这是基于 (a) 血小板肌动蛋白的 Kd 为 0.4-0.7 µ，其是通过新设计的更简单的方法制备的，以及 (b) 单体肌动蛋白和 Tj84 的浓度值，我们测量的值分别为 280 和 560 µ。使用较高的 Kd 值 0.7 µ，计算得出 T04 复合肌动蛋白介于 70 至 240 µ 之间，具体取决于稳态游离 G 肌动蛋白浓度。这可能在 0.1 至 0.5 µ 之间变化，这是未加帽和完全倒刺末端加帽的肌动蛋白丝的临界浓度。如果血小板中的 Kd 与体外相同，并且静息血小板中超过 95% 的肌动蛋白丝在其带倒刺的末端被覆盖，则大多数隔离的肌动蛋白将与 T/34 结合。
Revised Manuscript Received April 21, 1992 abstract: Quantitative measurements of the interactions of Tj84 with muscle actin suggest that its only physiological role is monomer sequestration. T/34 forms a 1: 1 complex with monomeric actin under physiological salt conditions. Its K¿ for actin is not affected by calcium. T¡ 84 binds only to actin monomers and not to filament ends or alongside the filament. T/? 4-actincomplexes do not elongate actin filaments at either the barbed or the pointed end, and, unlike actobindin, T/S4 does not specifically suppress the nucleation of polymerization. We assessed the fraction of monomeric actin that can be sequesteredby ß4 in resting platelets. This was done on the basis of (a) its Kd of 0.4-0.7 µ for platelet actin, which had been prepared by a newly devised simpler method, and (b) the values for the concentrations of monomeric actin and of Tj84 which we measured as 280 and 560 µ, respectively. Using the higher Kd value of 0.7 µ, the T04-complexed actin is calculated to be between 70 and 240 µ, depending on the steady-state free G-actin concentration. This may vary from 0.1 to 0.5 µ, the critical concentrations for uncapped and for fully barbed-end-capped actin filaments. If the Kd in the platelet is the same as in vitro, most of the sequestered actin would be bound to T/34 if more than 95% of the actin filaments are capped at their barbed ends in resting platelets.