Enzymatic joining of polynucleotides. XI. Reversal of Escherichia coli deoxyribonucleic acid ligase reaction.

Abstract Incubation of superhelical closed circular DNA with Escherichia coli DNA ligase and adenosine 5'-monophosphate (AMP) yields two new circular forms: molecules with one single strand break and covalently closed circles that have lost superhelical turns. This result, which is dependent on added AMP, shows that the joining reaction catalyzed by the DNA ligase is reversible. The use of radioactive AMP has permitted the identification of the ligase-AMP and DNA-adenylate intermediates in the reverse reaction.