Restriction of PM2 supercoiled DNA by Hap II endonuclease.

Restriction of the covalently closed circular DNA from phage PM2 (CCC PM2 DNA) by Hap II endonuclease was studied under varying enzyme concentration. At low Hap II concentration, accumulation of the intermediate product, OC DNA, was observed at the early stages of the reaction. The resulting final mixture of restriction products consists of OC and L DNA, and their relative content depends on the concentration of the enzyme used. The affinity of the enzyme for the intact recognition site of the substrate in different conformational forms does not seem to be affected. Basically identical results were obtained with the two different CCC DNA used: PM2 and SV40 DNA.