Structure of the DNA ligase-adenylate intermediate: lysine (epsilon-amino)-linked adenosine monophosphoramidate.

Proteolytic degradation of the Escherichia coli DNA ligase-adenylate intermediate releases adenosine 5'-monophosphate linked to the epsilon-amino group of lysine by a phosphoamide bond. Measurements of the rate of hydroxylaminolysis of the ligase-adenylate provide further support for a phosphoamide linkage in the native enzyme. Lysine (epsilon-amino)-linked adenosine monophosphoramidate has also been isolated from the T4 phage-induced ligase-adenylate intermediate. These results indicate that an initial step of the DNA ligase reaction consists of the nucleophilic attack of the epsilon-amino group of a lysine residue of the enzyme on the adenylyl phosphorus of DPN or ATP that leads to the formation of enzyme-bound lysine (epsilonamino)-linked adenosine monophosphoramidate.