Winder Steven J, Jess Thomas, Ayscough Kathryn R
Institute of Biomedical and Life Sciences, Davidson Building, University of Glasgow, Glasgow G12 8QQ, UK.
Biochem J. 2003 Oct 15;375(Pt 2):287-95. doi: 10.1042/BJ20030796.
The association of F-actin (filamentous actin) with a large number of binding proteins is essential for cellular function. Actin-binding proteins control the dynamics of actin filaments, nucleate new filaments and facilitate formation of higher-order structures such as actin bundles. The yeast gene SCP1 encodes a small protein with significant homology to mammalian SM22/transgelin. We have investigated the role of Scp1p in budding yeast to probe the fundamental role of this family of proteins. Here, we demonstrate that Scp1p binds to F-actin and induces the formation of tight F-actin bundles in vitro. Deletion of SCP1 in yeast lacking the actin-bundling protein, fimbrin (Sac6p), exacerbates the disrupted actin phenotype and enhances latrunculin-A sensitivity. Furthermore, Scp1p co-localizes with actin in cortical patches and its localization is lost in the presence of latrunculin-A. Our data support a role for Scp1p in bundling actin filaments and, in concert with Sac6p, acting as a second actin-bundling activity crucial to the stability of the yeast actin cytoskeleton.
F-肌动蛋白（丝状肌动蛋白）与大量结合蛋白的关联对细胞功能至关重要。肌动蛋白结合蛋白控制肌动蛋白丝的动态变化，使新的肌动蛋白丝成核，并促进高阶结构如肌动蛋白束的形成。酵母基因SCP1编码一种与哺乳动物SM22/转胶蛋白具有显著同源性的小蛋白。我们研究了Scp1p在芽殖酵母中的作用，以探究该蛋白家族的基本作用。在此，我们证明Scp1p在体外与F-肌动蛋白结合并诱导紧密的F-肌动蛋白束的形成。在缺乏肌动蛋白束蛋白fimbrin（Sac6p）的酵母中缺失SCP1，会加剧肌动蛋白表型的破坏并增强对latrunculin-A的敏感性。此外，Scp1p与肌动蛋白在皮质斑中共定位，并且在存在latrunculin-A的情况下其定位消失。我们的数据支持Scp1p在捆绑肌动蛋白丝方面的作用，并与Sac6p协同作用，作为对酵母肌动蛋白细胞骨架稳定性至关重要的第二种肌动蛋白捆绑活性。
