Janmey P A, Chaponnier C, Lind S E, Zaner K S, Stossel T P, Yin H L
Biochemistry. 1985 Jul 2;24(14):3714-23. doi: 10.1021/bi00335a046.
Gelsolin is a calcium binding protein that shortens actin filaments. This effect occurs in the presence but not in the absence of micromolar calcium ion concentrations and is partially reversed following removal of calcium ions. Once two actin molecules have bound to gelsolin in solutions containing Ca2+, one of the actins remains bound following chelation of calcium, so that the reversal of gelsolin's effect cannot be accounted for simply by its dissociation from the ends of the shortened filaments to allow for elongation. In this paper, the interactions with actin of the ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) stable 1:1 gelsolin-actin complexes are compared with those of free gelsolin. The abilities of free or complexed gelsolin to sever actin filaments, nucleate filament assembly, bind to the fast growing (+) filament ends, and lower the filament size distribution in the presence of either Ca2+ or EGTA were examined. The results show that both free gelsolin and gelsolin-actin complexes are highly dependent on Ca2+ concentration when present in a molar ratio to actin less than 1:50. The gelsolin-actin complexes, however, differ from free gelsolin in that they have a higher affinity for (+) filament ends in EGTA and they cannot sever filaments in calcium. The limited reversal of actin-gelsolin binding following removal of calcium and the calcium sensitivity of nucleation by complexes suggest an alternative to reannealing of shortened filaments that involves redistribution of actin monomers and may account for the calcium-sensitive functional reversibility of the solation of actin by gelsolin.
凝溶胶蛋白是一种能使肌动蛋白丝缩短的钙结合蛋白。这种效应在存在微摩尔浓度钙离子的情况下会发生，而在不存在钙离子的情况下则不会发生，并且在去除钙离子后会部分逆转。在含有Ca2+的溶液中，一旦两个肌动蛋白分子与凝溶胶蛋白结合，其中一个肌动蛋白在钙离子螯合后仍保持结合状态，因此凝溶胶蛋白效应的逆转不能简单地归因于它从缩短的丝末端解离以允许伸长。在本文中，将乙二醇双（β-氨基乙醚）-N，N，N'，N'-四乙酸（EGTA）稳定的1:1凝溶胶蛋白-肌动蛋白复合物与游离凝溶胶蛋白与肌动蛋白的相互作用进行了比较。研究了游离或复合凝溶胶蛋白在存在Ca2+或EGTA时切断肌动蛋白丝、引发丝组装、结合快速生长的（+）丝末端以及降低丝大小分布的能力。结果表明，当游离凝溶胶蛋白和凝溶胶蛋白-肌动蛋白复合物与肌动蛋白的摩尔比小于1:50时，它们都高度依赖于Ca2+浓度。然而，凝溶胶蛋白-肌动蛋白复合物与游离凝溶胶蛋白的不同之处在于，它们在EGTA中对（+）丝末端具有更高的亲和力，并且在钙存在时不能切断丝。去除钙后肌动蛋白-凝溶胶蛋白结合的有限逆转以及复合物对成核的钙敏感性表明，缩短的丝重新退火存在一种替代方式，即涉及肌动蛋白单体的重新分布，这可能解释了凝溶胶蛋白使肌动蛋白溶胶化的钙敏感功能可逆性。
