EcoR Ⅱ was the first restriction endonuclease ever found requiring the cooperative interaction with the least two DNA sites for digestion activity.To study the specific activity, Eco R Ⅱ was purified from hyperexpression engineering bacteria in which the specific expression products increased to about 20% of total cellular protein.By using chromatography on DEAE cellulose column,phosphocellulose column and FPLC of Resource Q,the enzyme was purified from soluble protein fraction.The inclusion bodies were solved and renatured,and the enzyme was purified from this part of protein with higher specific activity by using FPLC of Resource Q.Detection showed that the enzyme was purified to homogeneity and was free of detectable contamination by other DNase(exo and endo).
