Polypeptide structure of human terminal transferase

The polypeptide structure of terminal transferase purified from human lymphoblasts was examined with an immunoblot procedure using rabbit anti-calf thymus terminal transferase antibodies. Two doublets of bands of Mr 58-56,000 and Mr 44-42,000 are the major immunoreactive polypeptides. Only the Mr 44-42,000 polypeptides can be efficiently renatured after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Controlled degradation with trypsin produces fully active enzyme containing the ? and ? polypeptides typical of the low molecular weight terminal transferase, suggesting that the different forms of purified terminal transferase may arise by proteolysis of the Mr 58,000 polypeptide.