Espin contains an additional actin-binding site in its N terminus and is a major actin-bundling protein of the Sertoli cell-spermatid ectoplasmic specialization junctional plaque
Espin contains an additional actin-binding site in its N terminus and is a major actin-bundling protein of the Sertoli cell-spermatid ectoplasmic specialization junctional plaque
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DOI：
10.1091/mbc.10.12.4327
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发表时间：
1999-12-01
影响因子：
3.3
通讯作者：
Bartles, JR
中科院分区：
文献类型：
--
作者：
Chen, B;Li, AL;Bartles, JR
espins 是定位于平行肌动蛋白束的肌动蛋白结合和成束蛋白。支持细胞-精子细胞连接（胞质特化）的 837 个氨基酸“espin”和刷状缘微绒毛的 253 个氨基酸“小 espin”是剪接亚型，它们共享 C 端 116 个氨基酸肌动蛋白捆绑模块，但包含不同的 N 端。为了研究 espin 及其延伸的 N 末端的作用，我们检查了 espin 构建体的肌动蛋白结合和捆绑特性以及 espin 在外质特化中的化学计量和发育积累。与 F-肌动蛋白结合的 espin 构建体的亲和力比小 espin 高约三倍（K-d = 类似于 70 nM），并且形成束的效率大约高 2.5 倍。亲和力增加似乎是由于 espin N 末端有一个额外的肌动蛋白结合位点。这个额外的肌动蛋白结合位点以类似于 1 μM 的 K-d 与 F-肌动蛋白结合，修饰转染细胞中的肌动蛋白应力纤维样结构，并被定位到 espin N 末端两个富含脯氨酸的肽之间的肽。检测到的 Espin 类似于每个外质特化 4-5 x 10(6) 个拷贝，或者类似于每 20 个肌动蛋白单体 1 个 espin，并在那里积累，与精子发生过程中平行肌动蛋白束的形成一致。这些结果表明 espin 是支持细胞-精子细胞胞质特化的主要肌动蛋白捆绑蛋白。
The espins are actin-binding and -bundling proteins localized to parallel actin bundles. The 837-amino-acid "espin" of Sertoli cell-spermatid junctions (ectoplasmic specializations) and the 253-amino-acid "small espin" of brush border microvilli are splice isoforms that share a C-terminal 116-amino-acid actin-bundling module but Contain different N termini. To investigate the roles of espin and its extended N terminus, we examined the actin-binding and -bundling properties of espin constructs and the stoichiometry and developmental accumulation of espin within the ectoplasmic specialization. An espin construct bound to F-actin with an approximately threefold higher affinity (K-d = similar to 70 nM) than small espin and was similar to 2.5 times more efficient at forming bundles. The increased affinity appeared to be due to an additional actin-binding site in the N terminus of espin. This additional actin-binding site bound to F-actin with a K-d of similar to 1 mu M, decorated actin stress fiber-like structures in transfected cells, and was mapped to a peptide between the two proline-rich peptides in the N terminus of espin. Espin was detected at similar to 4-5 x 10(6) copies per ectoplasmic specialization, or similar to 1 espin per 20 actin monomers and accumulated there coincident with the formation of parallel actin bundles during spermiogenesis. These results suggest that espin is a major actin-bundling protein of the Sertoli cell-spermatid ectoplasmic specialization.