DNA ligase that seals nicks in double-stranded DNA during DNA replication, DNA recombination and DNA repair. Can use ATP, ADP and GTP, but not CTP, TTP or 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. Optimum pH is 8.0. Optimum temperature is 75 degrees Celsius. Belongs to the ATP-dependent DNA ligase family.