DNA ligase that seals nicks in double-stranded DNA during DNA replication, DNA recombination and DNA repair. Can use both ATP and ADP. 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. Inhibited by Ca(2+) and Zn(2+). Optimum pH is 6.5. Optimum temperature is 75 degrees Celsius. Activity declines at temperatures from 75 to 80 degrees Celsius. Belongs to the ATP-dependent DNA ligase family. Extended N-terminus. Extended N-terminus.