Differential sensitivity of low molecular weight DNA polymerase to sulfhydryl-blocking reagents

Abstract

Activity of a 2.5 S mouse myeloma DNA polymerase (termed DNA polymerase II) measured with either poly(rA) or poly(dA) as template did not require sulfhydryl-reducing reagents, but was sensitive to inhibition by p- hydroxymercuribenzoate and the sulfhydryl-alkylating reagent, N- ethylmaleimide ; however, the activity was much more sensitive to inhibition by p- hydroxymercuribenzoate than by the sulfhydryl-alkylating reagent. The p- hydroxymercuribenzoate inhibition appeared to involve the mercurial portion of the p- hydroxymercuribenzoate molecule because HgCl 2 was an equally effective inhibitor, while p- hydroxybenzoate had little effect upon enzyme activity. The p- hydroxymercuribenzoate inhibition was reversed by an equal concentration of the sulfhydryl-reducing reagent, dithiothreitol.