Two Species of DNA Polymerase Isolated from Escherichia coli

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Abstract
Two species of DNA polymerase were isolated from E. coli. By comparison with internal standards, l‐malate dehydrogenase and creatine kinase, in sucrose gradient centrifugation, the sedimentation coefficients were determined for DNA polymerase A, s20,w= 3.8 S, and DNA polymerase B, s20,w= 4.9 S. The enzymes dissociate upon Sephadex gel filtration and basic subunits of each species having estimated molecular weights of 30,000 and 54,000, respectively, are observed together with more associated forms with molecular weights up to 170,000 and 300,000. From immunological studies, a similar protein seems to be present in both species. The two enzymes are equal in template specificity but differ in their ability to initiate de novo synthesis of dAT copolymer.