Forrest G L, Klevecz R R
J Cell Biol. 1978 Aug;78(2):441-50. doi: 10.1083/jcb.78.2.441.
Tyrosyltubulin ligase (TTL) was found to be present in CHO and V79 Chinese hamster cells grown in tissue culture. The enzyme is soluble and requires potassium, magnesium, and ATP for maximum activity and requires tubulin as a substrate. TTL was analyzed through the cell cycle of V79 and CHO Chinese hamster cells. The enzyme showed two peaks of activity in V79 cells at 4 h and 7 h after mitotic selection, corresponding to the early S and mid to late S phases of the cell cycle. In CHO cells the enzyme displayed a major peak of activity at mid S and a minor peak or plateau during early S. Tubulin, as measured by (3H)colchicine binding, was shown to increase through S phase and reach a maximum late in the cycle during G2 approx. 3 h after maximum TTL activity.
在组织培养中生长的中国仓鼠卵巢(CHO)细胞和V79细胞中发现了酪氨酰微管蛋白连接酶(TTL)。该酶是可溶的,最大活性需要钾、镁和三磷酸腺苷(ATP),并且需要微管蛋白作为底物。通过V79细胞和中国仓鼠CHO细胞的细胞周期对TTL进行了分析。该酶在有丝分裂选择后4小时和7小时的V79细胞中显示出两个活性峰值,分别对应于细胞周期的早S期和中晚期S期。在CHO细胞中,该酶在S期中期显示出一个主要活性峰值,在S期早期显示出一个次要峰值或平台期。通过(3H)秋水仙碱结合测定的微管蛋白显示在S期增加,并在G2期接近细胞周期后期达到最大值,大约在TTL活性最大值后3小时。