The synthesis of polydeoxyribonucleotide by cell-free extracts of embryonic mouse tissue

Abstract

The conditions under which soluble extracts prepared from mouse embryos incorporate [H3]thymidine 5[image]-triphosphate into polydeoxyribonucleotide have been studied. In common with similar preparations from other mammalian tissues, mouse-embryo DNA nucleotidyltransferase requires the four complementary deoxyribonucleodise 5[image]-triphosphates, primer DNA and a bivalent cation for activity. Unlike other mammalian DNA nucleotidyltransferases, the rate and extent of the incorporation of [H3]thymidine 5[image]-triphosphate is much greater with Mn2+ than with Mg2+ and, with either Mg2+ or Mn2+, maximum activity occurs at pH 6.4. The difference between Mg2+ and Mn2+ varies markedly with pH, reaching a maximum of six- to eight-fold at pH 6.4.