Hertzog Maud, Yarmola Elena G, Didry Dominique, Bubb Michael R, Carlier Marie-France
Dynamique du Cytosquelette, Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, 91198 Gif-sur-Yvette, France.
J Biol Chem. 2002 Apr 26;277(17):14786-92. doi: 10.1074/jbc.M112064200. Epub 2002 Feb 20.
Actobindin is an actin-binding protein from amoeba, which consists of two beta-thymosin repeats and has been shown to inhibit actin polymerization by sequestering G-actin and by stabilizing actin dimers. Here we show that actobindin has the same biochemical properties as the Drosophila or Caenorhabditis elegans homologous protein that consists of three beta-thymosin repeats. These proteins define a new family of actin-binding proteins. They bind G-actin in a 1:1 complex with thermodynamic and kinetic parameters similar to beta-thymosins. Like beta-thymosins, they slow down nucleotide exchange on G-actin and make a ternary complex with G-actin and Latrunculin A. On the other hand, they behave as functional homologs of profilin because their complex with MgATP-G-actin, unlike beta-thymosin-actin, participates in filament barbed end growth, like profilin-actin complex. Therefore these proteins play an active role in actin-based motility processes. In addition, proteins of the actobindin family interact with the pointed end of actin filaments and inhibit pointed end growth, maybe via the interaction of the beta-thymosin repeats with two terminal subunits.
肌动蛋白结合蛋白是一种来自变形虫的肌动蛋白结合蛋白，它由两个β-胸腺素重复序列组成，并且已被证明可通过隔离G-肌动蛋白和稳定肌动蛋白二聚体来抑制肌动蛋白聚合。在这里我们表明，肌动蛋白结合蛋白具有与果蝇或秀丽隐杆线虫中由三个β-胸腺素重复序列组成的同源蛋白相同的生化特性。这些蛋白质定义了一个新的肌动蛋白结合蛋白家族。它们以1:1复合物的形式结合G-肌动蛋白，其热力学和动力学参数与β-胸腺素相似。与β-胸腺素一样，它们减缓G-肌动蛋白上的核苷酸交换，并与G-肌动蛋白和Latrunculin A形成三元复合物。另一方面，它们表现为肌动蛋白 Profilin 的功能同源物，因为它们与MgATP-G-肌动蛋白的复合物，与β-胸腺素-肌动蛋白不同，参与丝状肌动蛋白的刺端生长，就像Profilin-肌动蛋白复合物一样。因此，这些蛋白质在基于肌动蛋白的运动过程中发挥着积极作用。此外，肌动蛋白结合蛋白家族的蛋白质与肌动蛋白丝的尖端相互作用并抑制尖端生长，可能是通过β-胸腺素重复序列与两个末端亚基的相互作用实现的。
