InterPro: IPR018239 NAD-dependent DNA ligase, active site

DNA ligase (polydeoxyribonucleotide synthase) is the enzyme that joins two DNA fragments by catalyzing the formation of an internucleotide ester bond between phosphate and deoxyribose. It is active during DNA replication, DNA repair and DNA recombination. There are two forms of DNA ligase: one requires ATP (EC:6.5.1.1), the other NAD (EC:6.5.1.2).

This family is predominantly composed of NAD-dependent bacterial DNA ligases. They are proteins of about 75 to 85 Kd whose sequence is well conserved [1, 2]. They also show similarity to yicF, an Escherichia coli hypothetical protein of 63 Kd.

This entry contains two signature patterns for this family of proteins; these signatures are based on conserved regions in the N-terminal half. The first of which (DNA_LIGASE_N1) contains the KXDG motif required for adenylation of eukaryotic DNA ligases. The lysine residue being required for the adenylation step of the ligase and the aspartate being required for the de-adenylation step [3, 4].