[Formation of two types of enzyme-substrate complexes during the interaction of EcoRII restriction enzyme with synthetic DNA-duplexes].

Binding of EcoRII restriction endonuclease to synthetic oligodeoxyribonucleotide substrates of 11-30 base pairs long was investigated by polyacrylamide gel electrophoresis under nondenaturing conditions in the absence of Mg2+ ions. Irrespective of the length of a substrate, two types of specific DNA-protein complexes were shown to be formed. Their mobility in gel was close to that of the monomer (45 kDa) and dimer (90 kDa) of marker protein, ovalbumin. The ratio of these complexes in solution depended on that of the molar concentrations of EcoRII restriction endonuclease and DNA duplexes. The possible structure of the complexes is discussed.