Terminal Deoxynucleotidyl Transferase (TdT), a template-independent DNA polymerase, catalyzes the repetitive addition of deoxyribonucleotides to the 3'-OH of oligodeoxyribonucleotides and single-stranded and double-stranded DNA. TdT requires an oligonucleotide of at least three nucleotides to serve as a primer. With RNA as template TdT shows variable performance which strongly depends upon the tertiary structure of acceptor RNA 3'-end and the nature of nucleotide. Generally, it is lower than using DNA as a template.
- Incorporates modified nucleotides (e.g., fluorescein-, biotin-, aminoallyl-labeled nucleotides)
|metal chelators, ammonium, chloride, iodide, phosphate ions|
|E. coli cells carrying a cloned gene encoding calf thymus terminal deoxynucleotidyl transferase|