DNA polymerase activities of bacteria grown in media containing zinc ions.

Abstract

Bacterial DNA Polymerase I is a zinc metalloenzyme. The origin of the intrinsic zinc atom of the enzyme is from zinc ions contaminated in synthetic growth media. Removal of zinc ion by low concentrations of o-phenanthroline shows strong inhibition of bacterial growth. DNA Polymerase activity of bacterial cells grown in synthetic media supplemented with zinc sulfate (10-6M) is 3-8 fold higher than that of bacteria grown in non-zinc supplemented media. However growth rates of the bacterial cells in zinc supplemented and non-zinc supplemented media showed no difference, suggesting that DNA polymerase activities per cell in zinc supplemented media is higher than that in non-zinc supplemented media. These differences in activity may be due to a qualitative difference in the enzyme activity rather than a quantitative difference in bacterial DNA polymerase molecules. Heat stability of DNA polymerase activity from zinc supplemented culture far exceeds that from non-zinc supplemented culture. Results of the heat stability tests indicate that the activity of each enzyme molecule is increased. It is suggested that the qualitative difference of this enzyme is due to the incorporation of more than one zinc ion into the enzyme molecule with a resulting conformational change.