Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA.
J Biol Chem. 2013 Aug 2;288(31):22324-32. doi: 10.1074/jbc.M113.458406. Epub 2013 Jun 20.
It is unknown whether homologs of the cadherin·catenin complex have conserved structures and functions across the Metazoa. Mammalian αE-catenin is an allosterically regulated actin-binding protein that binds the cadherin·β-catenin complex as a monomer and whose dimerization potentiates F-actin association. We tested whether these functional properties are conserved in another vertebrate, the zebrafish Danio rerio. Here we show, despite 90% sequence identity, that Danio rerio and Mus musculus αE-catenin have striking functional differences. We demonstrate that D. rerio αE-catenin is monomeric by size exclusion chromatography, native PAGE, and small angle x-ray scattering. D. rerio αE-catenin binds F-actin in cosedimentation assays as a monomer and as an α/β-catenin heterodimer complex. D. rerio αE-catenin also bundles F-actin, as shown by negative stained transmission electron microscopy, and does not inhibit Arp2/3 complex-mediated actin nucleation in bulk polymerization assays. Thus, core properties of α-catenin function, F-actin and β-catenin binding, are conserved between mouse and zebrafish. We speculate that unique regulatory properties have evolved to match specific developmental requirements.
尚不清楚黏附素·连环蛋白复合体的同源物是否在后生动物界具有保守的结构和功能。哺乳动物αE-连环蛋白是一种变构调节的肌动蛋白结合蛋白，以单体形式结合黏附素·β-连环蛋白复合体，其二聚化增强 F-肌动蛋白的结合。我们测试了这些功能特性是否在另一种脊椎动物斑马鱼 Danio rerio 中保守。尽管序列同一性为 90%，但我们在此显示，斑马鱼和小鼠的αE-连环蛋白具有显著的功能差异。我们通过大小排阻色谱、天然 PAGE 和小角度 X 射线散射证明了 D. rerio αE-连环蛋白是单体。D. rerio αE-连环蛋白在共沉淀测定中以单体和α/β-连环蛋白异二聚体复合物的形式结合 F-肌动蛋白。D. rerio αE-连环蛋白也通过负染透射电子显微镜显示出 F-肌动蛋白的束状，并且在批量聚合测定中不抑制 Arp2/3 复合物介导的肌动蛋白成核。因此，α-连环蛋白功能的核心特性，即 F-肌动蛋白和β-连环蛋白结合，在小鼠和斑马鱼之间是保守的。我们推测，独特的调节特性已经进化以适应特定的发育需求。
