Mechanism of the interaction of human platelet profilin with actin.
Mechanism of the interaction of human platelet profilin with actin.
复制标题
人血小板与肌动蛋白相互作用的机制。
DOI：
10.1083/jcb.113.5.1081
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发表时间：
1991-06
影响因子：
7.8
通讯作者：
Pollard, T D
中科院分区：
文献类型：
--
作者：
Goldschmidt-Clermont, P J;Machesky, L M;Doberstein, S K;Pollard, T D
我们重新研究了纯化的血小板profilin与肌动蛋白的相互作用，并提出证据表明，简单的螯合肌动蛋白单体在1：1复合物与profilin不能解释许多profilin对肌动蛋白组装的影响。评估profilin与肌动蛋白结合的三种不同方法表明，与血小板肌动蛋白的复合物具有1至5 μ M范围内的解离常数。肌肉肌动蛋白的值类似。当与肌动蛋白结合时，profilin使ATP从肌动蛋白解离的速率常数增加1，000倍，并且还增加与肌动蛋白结合的Ca 2+的解离速率。动力学模拟表明，profilin交换肌动蛋白单体之间的亚秒级的时间尺度，使其能够催化核苷酸交换。另一方面，聚合试验给出了不同的结果，是不一致的结合试验和彼此：profilin有不同的影响，在肌动蛋白丝的两端伸长; profilin抑制血小板肌动蛋白的伸长比肌肉肌动蛋白更强烈;和简单的形成1：1复合物的肌动蛋白与profilin不能解释自发聚合的强烈抑制。我们认为，在体外对肌动蛋白聚合的影响可能是由一个复杂的机制，包括弱帽丝端和催化中毒的成核。虽然血小板中每5-10个肌动蛋白分子仅含有1个profilin，但这些复杂的反应可能使亚化学计量的profilin对肌动蛋白组装产生重要影响。我们也证实了I.拉辛和你。Lindberg（1985.自然[伦敦] 318：472- 474），聚磷酸肌醇抑制了前纤维蛋白对肌动蛋白聚合的作用，因此当考虑前纤维蛋白在细胞中的功能时，还必须考虑脂质代谢。
We have reexamined the interaction of purified platelet profilin with actin and present evidence that simple sequestration of actin monomers in a 1:1 complex with profilin cannot explain many of the effects of profilin on actin assembly. Three different methods to assess binding of profilin to actin show that the complex with platelet actin has a dissociation constant in the range of 1 to 5 microM. The value for muscle actin is similar. When bound to actin, profilin increases the rate constant for dissociation of ATP from actin by 1,000-fold and also increases the rate of dissociation of Ca2+ bound to actin. Kinetic simulation showed that the profilin exchanges between actin monomers on a subsecond time scale that allows it to catalyze nucleotide exchange. On the other hand, polymerization assays give disparate results that are inconsistent with the binding assays and each other: profilin has different effects on elongation at the two ends of actin filaments; profilin inhibits the elongation of platelet actin much more strongly than muscle actin; and simple formation of 1:1 complexes of actin with profilin cannot account for the strong inhibition of spontaneous polymerization. We suggest that the in vitro effects on actin polymerization may be explained by a complex mechanism that includes weak capping of filament ends and catalytic poisoning of nucleation. Although platelets contain only 1 profilin for every 5-10 actin molecules, these complex reactions may allow substoichiometric profilin to have an important influence on actin assembly. We also confirm the observation of I. Lassing and U. Lindberg (1985. Nature [Lond.] 318:472- 474) that polyphosphoinositides inhibit the effects of profilin on actin polymerization, so lipid metabolism must also be taken into account when considering the functions of profilin in a cell.