E. coli DNA Ligase is a ligation enzyme that can be used to join DNA fragments by catalyzing the formation of phosphodiester bonds between double-stranded DNA fragmentscontaining juxtaposed 5"-phosphate termini and 3"-hydroxyl terminiin the presence of the NAD cofactor. Both E.coli DNA Ligase and T4 DNA Ligase are used in gene cloning experiments; however, E. coli DNA Ligase can only catalyze ligation ofcohesive end-containing DNA fragments via standard reaction conditions.