Cyclic AMP-dependent phosphorylation of terminal deoxynucleotidyl transferase.

Incubation of human lymphoblastoid cell extracts in the presence of cAMP and ATP produces changes in the chromatographic pattern of terminal transferase activity separated on phosphocellulose columns. Incubation of high molecular weight and low molecular weight preparations of calf thymus terminal transferase with the catalytic subunit of beef cardiac muscle cAMP-dependent protein kinase and [gamma-32P]ATP result in phosphorylation of the 58,000-dalton form of the enzyme and no other lower molecular weight terminal peptides. These results, taken with our earlier results on tissue proteolysis of terminal transferase to lower molecular weight, active forms (Chang, L. M. S., Plevani, P., and Bollum, F. J. (1982) J. Biol. Chem. 257, 5700-5706), resolve the heterogeneity observed with various preparations of the enzyme.