Peculiarities of the binding of restriction endonuclease EcoRII to synthetic DNA duplexes.

The binding of restriction endonuclease EcoRII to synthetic oligodeoxyribonucleotide substrates 11 to 30 bp long was investigated by gradient polyacrylamide gel electrophoresis under nondenaturing conditions in the absence of Mg2+ ions. Irrespective of the substrate's length, two types of specific DNA-protein complexes were shown to be formed. Their mobility in gel was close to that of the monomer and the dimer of the marker ovalbumin. The number of such complexes in solution depended on the ratio of the molar concentrations of restriction endonuclease EcoRII and the DNA duplex. The possible structure of the complexes is discussed.