DNA ligase that seals nicks in double-stranded DNA during DNA replication, DNA recombination and DNA repair. Can also use ADP, but not NAD(+). ATP + (deoxyribonucleotide)n-3'-hydroxyl + 5'-phospho-(deoxyribonucleotide)m = (deoxyribonucleotide)n+m + AMP + diphosphate. ADP + (deoxyribonucleotide)n-3'-hydroxyl + 5'-phospho-(deoxyribonucleotide)m = (deoxyribonucleotide)n+m + AMP + phosphate. GTP + (deoxyribonucleotide)n-3'-hydroxyl + 5'-phospho-(deoxyribonucleotide)m = (deoxyribonucleotide)n+m + GMP + diphosphate. Less active with Ca(2+) or Co(2+). Not active with Cu(2+), Zn(2+), Sr(2+) or Ni(2+). Inhibited in the presence of 100 mM KCl, NaCl or NH(4)Cl. Optimum pH is 7.5. Optimum temperature is 70 degrees Celsius. Monomer. Belongs to the ATP-dependent DNA ligase family.