Tyrosyltubulin ligase and colchicine binding activity in synchronized Chinese hamster cells.

Abstract

Tyrosyltubulin ligase (TTL) was present in CHO and V79 Chinese hamster cells grown in tissue culture. The enzyme is soluble and requires K, Mg 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 2 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, increased through S phase and reach a maximum late in the cycle during G2 approximately 3 h after maximum TTL activity.