In vitro conversion of a calf thymus 8S DNA polymerase to a 7.3S species

Abstract

MULTIPLE species of calf thymus high molecular weight (6–8S) DNA polymerase have been distinguished by DEAE-cellulose chromatography and partially characterised^1–4. In order of elution these were designated enzymes A(8S), B(5.2S) and C(7.3S), and preliminary estimations indicated molecular weights of 200 × 10³–230 × 10³, 100 × 10³–110 × 10³ and 155 × 10³–175 × 10³ respectively¹. Subsequent experiments have resolved the A enzyme into two components, A₁ and A₂, eluting between 55 and 75 mM and 75 and 95 mM potassium phosphate pH 7.8, respectively (Fig. 1 and ref. 2). The relative levels of activity of A₁, A₂, B and C vary considerably in different preparations and we show here that on urea treatment, A₂ (sedimenting at around 8S), is converted into a species sedimenting at 7.3S, the sedimentation coefficient of the C species.