Kake T, Kimura S, Takahashi K, Maruyama K
Department of Biology, Faculty of Science, Chiba University, Japan.
Biochem J. 1995 Dec 1;312 ( Pt 2)(Pt 2):587-92. doi: 10.1042/bj3120587.
Calponin from chicken gizzard induced polymerization of actin in the presence of 10 mM KCl. Only 2 min after the addition of KCl in the presence of a 0.0625-0.25:1 molar ratio of calponin to actin, a Poisson-type length distribution (with an average length of approx. 0.7 micron) was observed with formed actin filaments. This result suggests that calponin-actin complexes served as nuclei for rapid elongation. Calponin caused a rapid polymerization of actin even in G-buffer (2 mM Tris/HCl, pH 8.0) which is usually used for depolymerization of actin filaments. Binding of calponin at a level of up to 1.25 mol per mol of actin was observed in the actin filaments formed in the presence of calponin at very low ionic strengths. When actin filaments were exposed to 3.3 mM KCl, by dilution with G-buffer, a rapid depolymerization occurred. Addition of calponin greatly retarded the depolymerization process and, in the presence of an equimolar ratio of calponin to actin, depolymerization hardly occurred. In the presence of calmodulin, this inhibitory effect on depolymerization was reversed by Ca2+, releasing calponin from actin filaments.
来自鸡肫的钙调蛋白在10 mM KCl存在的情况下诱导肌动蛋白聚合。在钙调蛋白与肌动蛋白的摩尔比为0.0625 - 0.25:1且存在KCl的情况下，加入KCl仅2分钟后，就观察到形成的肌动蛋白丝呈现泊松型长度分布（平均长度约为0.7微米）。这一结果表明钙调蛋白 - 肌动蛋白复合物作为快速伸长的核。即使在通常用于肌动蛋白丝解聚的G缓冲液（2 mM Tris/HCl，pH 8.0）中，钙调蛋白也能引起肌动蛋白的快速聚合。在极低离子强度下，在有钙调蛋白存在时形成的肌动蛋白丝中，观察到钙调蛋白与肌动蛋白的结合水平高达每摩尔肌动蛋白1.25摩尔。当肌动蛋白丝通过用G缓冲液稀释而暴露于3.3 mM KCl时，会发生快速解聚。加入钙调蛋白极大地延缓了解聚过程，并且在钙调蛋白与肌动蛋白等摩尔比的情况下，几乎不发生解聚。在存在钙调蛋白的情况下，Ca2 +会逆转这种对解聚的抑制作用，使钙调蛋白从肌动蛋白丝上释放出来。
