Immunological detection of a conserved structure for terminal deoxynucleotidyltransferase

The polypeptide structure of terminal transferase in crude extracts of thymus or cultured cells was examined by electrophoresis on polyacrylamide gels in the presence of sodium dodecyl sulfate, electrophoretic transfer of separated peptides to nitrocellulose, specific labeling with rabbit anti-calf thymus terminal transferase, and visualization with an immunoperoxidase reaction. The major form of terminal transferase detected in crude extracts or enzyme fractions after phosphocellulose chromatography is a single 58,000- to 60,000-dalton peptide for calf thymus, rat thymus, mouse thymus, chicken thymus, cat thymus, human lymphoblastoid cells, and mouse lymphoblastoid cells. Since the anti-calf thymus terminal transferase antibody was prepared against a homogeneous calf thymus enzyme consisting of two polypeptide chains in a hydrodynamic structure of Mr = 32,000, these results suggest that the homogeneous calf thymus enzyme preparation is a proteolytically degraded form of the 58,000-dalton peptide. Terminal transferase peptides from human, bovine, rat, chicken, cat, and mouse are immunologically related and have similar conserved polypeptide structure.