A deoxyribonucleic acid ligase from nuclei of rat liver. Purification and properties.

A DNA ligase has been extensively purified from nuclei of rat livers. The ligase seals single strand nicks in DNA with any of the four usual bases on either the 3 or 5 sides. It requires ATP and a divalent cation (Mg-2plus or Mn-2plus) for activity. At low Mg-2plus concentrations the activity is greatly stimulated by a variety of monovalent cations. Relatively small excesses of either monovalent or divalent cation above the amounts which give maximal activity lead to inhibition of activity. Poly(G) and poly(I) inhibit ligase activity; several other polyribonucleotides are not inhibitory. Low concentrations of inorganic pyrophosphate are inhibitory. The molecular weight of the ligase is estimated from gel filtration to be about 10 times 10-4.