Mechanism of o-phenanthroline mediated inhibition of E. coli DNA polymerase I : formation of template-primer-metal-phenanthroline complexes with resultant loss of catalytic activity.

Inhibition of E. coli DNA polymerase I activity by 1,10 phenanthroline in the absence of reducing agents requires a high concentration of inhibitor (1-10 mM) depending upon the template primer used to direct the synthesis. We find that o-phenanthroline, unlike its non-chelating analogue, forms a divalent cation mediated complex with template-primers. Enzyme bound to such complexes is unable to catalyse either polymerization or nuclease functions.