A Comparative Study on the Recovery of EcoRI Endonuclease from Two Different Genetically Modified Strains of Escherichia coli

Restriction enzymes have extensive applications in recombinant DNA technology. They are used in the preparation of recombinant molecules, and they provide an attractive system for the analysis of sequence specific DNA-protein interactions. Escherichia coli RI (EcoRI) endonuclease is a well-known restriction enzyme that recognizes the symmetrical hexanucleotide sequence GAATTC on duplex DNA and cleaves each strand between G and A residues . Physical and catalytic properties of EcoRI restriction endonuclease have been extensively studied by several groups and different purification protocols have been described1−9. In addition to the natural overproducer of EcoRI, E. coli RY13, genetically modified overproducing strains were also used to produce the enzyme. The gene encoding EcoRI endonuclease was placed under the control of the λpL promoter in these genetically modified, overproducing strains. The application of different purification protocols made it difficult to compare the yield and the quality of these strains in the production of EcoRI. ∗Present Address: Department of Molecular Biology and Genetics Faculty of Sciences and Letters, İstanbul Technical University, 80626 İstanbul-TURKEY