On the mechanism of inhibition by fluoride ions of the DNA polymerase reaction

Abstract

1. 1. In the presence of Mg 2+, the DNA polymerase reaction was inhibited about 90 percent by 0.16 M F −. However, in the presence of Mn 2+ instead of Mg 2+, F − had no inhibitory effect even at a concentration of 0.33 M. 2. 2. A precipitable radioactive complex was formed when Mg 2+, the substrates dATP, dGTP, dCTP and [ 3H]dTTP and F − were incubated with or without DNA polymerase. No precipitable complex was formed when Mn 2+ was used instead of Mg 2+. Thus, F − inhibition of DNA polymerase activity is probably due to formation of insoluble complexes containing Mg 2+, deoxynucleosidetriphosphates and F −. 3. 3. The formation of precipitable F − complexes was dependent on the presence of Mg 2+ and a phosphate compound. Nucleoside triphosphates, inorganic tripolyphosphate and pyrophosphate formed complexes with Mg 2+ and F − to a larger extent than did nucleoside monophosphates and orthophosphate. Nucleoside diphosphates seem to have an intermediary position in this respect. 4. 4. The velocity of formation of precipitable complexes increased with increasing Mg 2+ and F − concentrations and decreased at low pH or at low temperatures.