Pyrrolopyrimidine nucleotides and protein synthesis.

The interaction of amino pyrrolopyrimidine nucleotides with enzymes catalyzing different steps in the reaction sequence leading to the incorporation of amino acids into polypeptides has been studied. None of the analogue nucleotides could function as the energy source for activation of amino acids or esterification of transfer RNA (tRNA) by mammalian or bacterial enzymes. Toyocamycin S’-triphosphate and sangivamycin 5’4riphosphate were competitive inhibitors of the reactions catalyzed by mammalian enzymes. Tubercidin St&phosphate, toyocamycin 5’-triphosphate, and sangivamycin 5’4riphosphate were effective substrates for rabbit liver tRNA with adenosine nucleoside terminus pyrophosphorylase; the corresponding nucleosides were incorporated at the 3’ termini of tRNA, and the amino acid acceptor and transfer activities of the analogue-containing polynucleotides were studied. tRNA molecules with tubercidin termini were near normal in these respects, whereas the acceptor activities of tRNA molecules with sangivamycin and toyocamycin termini were greatly diminished. The coding properties of several tubercidin-containing polyribonucleotides were indistinguishable from those of the corresponding polymers containing adenosine.