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. Author manuscript; available in PMC: 2013 Nov 6.
Published in final edited form as: Transl Cancer Res. 2013 Jun;2(3):1219.

Figure 1.

Figure 1

Steps in the DNA ligation reaction. (I) The catalytic region of the DNA ligase consisting of the DNA binding domain (DBD, red), adenylation domain (AdD, green) and oligonucleotide/oligosaccharide binding-fold (OB-Fold, yellow), interacts with ATP to adenylate an active site lysine within the adenylation domain (AdD, green), releasing pyrophosphate; (II) When the adenylated ligase recognizes and binds to a DNA nick, it undergoes a conformational change such that the DBD, AdD and OB-fold encircle the nick. Within this compact structure, the AMP moiety is transferred from the ligase polypeptide to the 5' phosphate of the nick; (III) The non-adenylated ligase polypeptide utilizes the 3' hydroxyl terminus of the nick as a nucleophile to attack the 5' DNA-adenylate, resulting in phosphodiester bond formation and the release of the ligase polypeptide and AMP