Terminal deoxynucleotidyl transferase catalyzes the reaction of DNA phosphorylation.

The reaction of phosphorylation and phosphonylation of an oligodeoxynucleotide 3'-terminal hydroxyl (oligodeoxynucleotidyl kinase activity) catalyzed by calf thymus terminal deoxynucleotidyl transferase (TDT) was found. Triphosphates modified at Palpha-, Palpha,gamma- or Palpha,beta,gamma-residues served as low-molecular weight substrates. The reaction was TDT specific; human DNA polymerasesalphaandbeta, as well as AMV reverse transcriptase did not catalyze it.

Interactions of the HIV-1 reverse transcriptase 'AZT-resistant' mutant with substrates and AZT-TP.

To investigate the biochemical basis of the HIV-1 resistance to AZT we obtained the RT mutant containing four amino acid substitutions by an oligonucleotide-directed mutagenesis technique. Enzymatic properties of the wild type and mutant RTs were compared. 'AZT-resistant' mutations in RT were shown to be associated with the reduced capability of AZT-TP to block the DNA- but not RNA-directed DNA synthesis.