Skoufias D A, Wilson L
Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara 93106, USA.
Arch Biochem Biophys. 1998 Mar 1;351(1):115-22. doi: 10.1006/abbi.1997.0510.
The posttranslational removal and readdition of tyrosine at the C-terminus of alpha-tubulin is associated with generation of microtubule populations that differ in intracellular distributions, turnover rates, and sensitivities to microtubule-depolymerization agents. Here, we compared the in vitro assembly and colchicine binding characteristics of tubulin dimer preparations composed of alpha-tubulin that had been maximally tyrosinated (approximately 40% tyrosinated) by tubulin-tyrosine ligase and maximally detyrosinated (100% detyrosinated) by carboxypeptidase A. Maximally tyrosinated and detyrosinated tubulins had similar critical concentrations for polymerization and similar association constants for colchicine binding. Microtubules polymerized from the two tubulins also had similar steady-state mean lengths and length distributions. The growing and shortening dynamics (dynamic instability parameters) of individual microtubules made from maximally tyrosinated or detyrosinated alpha-tubulin as determined by video-enhanced dark-field microscopy were similar, but subtle differences in the growing and shortening rates were found. On balance, however, the dynamicity and thus the overall kinetic stability of the two microtubule populations were indistinguishable. The results support the idea that detyrosination of alpha-tubulin does not by itself generate stable microtubules.
α-微管蛋白C末端酪氨酸的翻译后去除和重新添加与微管群体的产生有关，这些微管群体在细胞内分布、周转率以及对微管解聚剂的敏感性方面存在差异。在此，我们比较了由微管蛋白酪氨酸连接酶使其酪氨酸化程度达到最大（约40%酪氨酸化）的α-微管蛋白和由羧肽酶A使其去酪氨酸化程度达到最大（100%去酪氨酸化）的α-微管蛋白组成的微管蛋白二聚体制剂的体外组装和秋水仙碱结合特性。酪氨酸化程度达到最大和去酪氨酸化程度达到最大的微管蛋白具有相似的聚合临界浓度和相似的秋水仙碱结合缔合常数。由这两种微管蛋白聚合形成的微管也具有相似的稳态平均长度和长度分布。通过视频增强暗场显微镜测定，由酪氨酸化程度达到最大或去酪氨酸化程度达到最大的α-微管蛋白构成的单个微管的生长和缩短动力学（动态不稳定性参数）相似，但在生长和缩短速率上发现了细微差异。然而，总体而言，这两种微管群体的动态性以及因此的整体动力学稳定性是无法区分的。这些结果支持了α-微管蛋白去酪氨酸化本身不会产生稳定微管的观点。
