Inhibitor studies of phage T4 wild‐type and mutant DNA polymerase. IV. The substrate analog 3′‐fluorothymidine 5′‐triphosphate

Abstract The deoxythymidine5′‐triphosphate (dTTP) analog 3′‐fluorothymidine 5′‐triphosphate (3′‐FdTTP) inhibits DNA synthesis by T4 wild‐type, L98 (mutator) and CB121 (antimutator) DNA polymerase. CB121 DNA polymerase is less sensitive by a factor of two than the L98 and T4 + enzymes. Inhibition is not due to incorporation of the analog into DNA. 3′‐FdTTP acts competitively to the substrate dTTP. The CB121 polymerase exhibits a higher K i to K m ratio than the other two enzymes (5.3 vs. 3.3) and thus discriminates better between the substrate dTTP and its analog 3′‐FdTTP. 3′‐FdTTP inhibits the polymerase‐associated 3′‐5′ exonuclease activities to the same extent as their polymerase activities. The CB121 3′‐5′ exonuclease activity is suppressed only half as much by 3′‐FdTTP as by dTTP. The results are discussed in relation to the role of T4 DNA polymerase and its associated 3′‐5′ exonuclease in determining the accuracy of DNA replication.