On the role of deoxyribonucleic acid polymerase in determining mutation rates. Characterization of the defect in the T4 deoxyribonucleic acid polymerase caused by the ts L88 mutation.

摘要: Abstract The T4 bacteriophage DNA polymerase mutant ts L88 has an unusually high mutation rate and is temperature-sensitive for synthesis. been purified to homogeneity compared the wild type with respect in vitro 3' 5' exonuclease activity, also frequency of utilizing deoxynucleoside triphosphates that are not complementary homopolymer templates. For latter, assay used measures only stable misincorporation, but detects any noncomplementary nucleotide incorporated subsequently hydrolyzed by polymerase-associated exonuclease, resulting formation monophosphate derived from triphosphate substrate. A specific defect was found ability enzyme discriminate against utilization dGTP dCTP when poly(dA)·poly(dT) as template. These substrates were utilized at 6 times amount dATP dTTP nearly same type. two enzymes equally efficient excising residues during reaction. On other hand, a template which four complementary, no difference recognition bases detectable. Thus, T7 both dTMP, dGMP, dCMP about dAMP. During this reaction newly added dAMP 2 4 frequently dTMP more than 10 often residues. Another noncomplementary, seen rates function temperature. There marked increase substrate between 25 30° enzyme. Neither showed such stimulation over temperature range nucleotide. activity much unstable assayed its activity. It concluded mutator characteristics result greater