Partial purification and characterization of DNA polymerases from the cauliflower inflorescence.

Abstract

Two distinct DNA polymerases, designated A and B, were partially purified from rapidly growing apical tissues of the cauliflower inflorescence (Brassica oleracea, var. botrytis). They were readily separable from each other, because enzyme A was adsorbable on an anion-exchanger but enzyme B was not. The effects of divalent cations and ionic strength on both enzyme activities were very different. Enzyme A utilized activated DNA well at low concentration of MgCl2 or at low ionic strength, but heart-denatured DNA was utilized more effectively than was activated DNA at a high concentration of MgCl2. Enzyme B also utilized much more heat-denatured DNA and poly(rA) .cntdot. (dT)10 at high ionic strength. Gel chromatography with Sephadex G-200 revealed that enzyme A has a higher MW (approximately 100,000) than enzyme B (approximately 75,000). Some points of properties in enzyme A and B resemble those of the 2 DNA polymerase-.alpha. and -.beta. from mammalian cells, respectively. The existence of the 3rd enzyme, designated C, in the fraction with enzyme A was suggested with an assay system using poly(rA) .cntdot. (dT)10 as the template.