USE OF DEOXYRIBONUCLEOSIDE TRIPHOSPHATES BY MUTANT FORMS OF T7 RNA-POLYMERASE

Mutant forms of T7 RNA polymerase able to use both rNTP and dNTP as su bstrates were studied. The mutant Tyr639Phe,Ser641Ala can efficiently synthesize mixed polymers containing one or two deoxyribonucleotides. The mutant Tyr639Phe exhibits this property to a lower extent (no more than one deoxyribonucleotide per strand) and is practically incapable of using dGTP. The efficiency of deoxyribonucleotide utilization on t he templates used in this work decreases in the order dCTP > dTTP > dA TP similar to dGTP. Initiation of RNA strand synthesis is the most ess ential for dNTP utilization.