Role of chloride ion in the dynamics of microtubule

微管是真核细胞中最基本的细胞骨架系统。微管是由α-和β-微管蛋白的异源二聚体组装而成的圆柱形聚合物，其在体外由亚基组装需要GTP（只有GTP结合形式的β-微管蛋白可以组装成聚合物，并且GTP在组装后立即水解为GDP）。在这项研究中，我们研究了各种阴离子，特别是氯离子，在微管蛋白的聚合和GTdR活性中的作用。不同阴离子对微管聚合的影响在Cl^-、F^-和葡萄糖酸盐存在下，观察到有效的体外微管聚合。在Br^-、NO_3^-和I^-存在下，聚合反应弱.微管蛋白的GTP酶活性在Br^-、NO_3^-存在时活性较高，Cl^-、F^-和葡萄糖酸盐存在时活性较低，表明Cl ^-、F ^-和葡萄糖酸盐等阴离子通过抑制微管蛋白的GTP酶活性而促进微管的聚合。

Microtubules are fundamental cytoskeletal systems in eukaryotic cells. Microtubule, assembled from heterodimers of α- and β-tubulin, are cylindrical polymers whose in vitro assembly from subunits requires GTP (only GTP-bound form of β-tubulin can assembled into polymer and GTP is hydrolysed to GDP just after assembly). In this study, we investigated the role of various anions, especially chloride ion, in polymerization and GTPase activity of tubulin.1. The effect of various anions on microtubule polymerizationIn the presence of Cl^-, F^- and gluconate, effective in vitro microtubule polymerization was observed. In the presence of Br^-, NO_3^-, or I^-, weak polymerizaion was observed.2. The effect of various anions on tubulin GTPase activiyGTPase activiy of tubulin was measured, and found that high activity was observed in the presence of Br^- or NO_3^-, and weak activiy was observed in the presence of Cl^-, F^- and gluconate.These observations indicated that some anions such as Cl^-, F^- and gluconate promoted polymerization of microtubules, via suppression of GTPase activity of tubulin.