title: Positive co-operative interaction between the subunits of CeqI restriction endonuclease.
abstract: CeqI restriction endonuclease, an isoschizomer of EcoRV, forms complexes of 12-20 subunits under physiological conditions, in the absence of DNA. These molecules partially dissociate in the presence of DNA sequences recognized by CeqI or in the presence of non-ionic detergents. In solutions containing high concentrations of salts (e.g. 1 M-NaCl), the enzyme dissociates into subunits, concomitantly losing its activity. According to our experiments, it is the tetrameric form of the enzyme that binds the DNA and represents the catalytically active molecule. Analysis of the enzyme kinetics revealed a positive co-operative interaction between the subunits of the enzyme. Computer-assisted analysis of these data yielded a Hill coefficient of approx. 1.35, suggesting two binding sites per tetrameric enzyme molecule, two subunits per palindromic recognition site.
authors.affiliation: Institute of Biochemistry, Biological Research Center of the Hungarian Academy of Sciences, Szeged.
authors.forename: Z
authors.initials: Z
authors.lastname: Jobbágy
authors.forename: Z
authors.initials: Z
authors.lastname: Izsvák
authors.forename: E
authors.initials: E
authors.lastname: Duda
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D002850:Chromatography, Gel; D003352:Corynebacterium / Q000201:enzymology*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008274:Magnesium / Q000494:pharmacology; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D013379:Substrate Specificity
chemical_list: D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides; D015252:Deoxyribonucleases, Type II Site-Specific; C027440:GATATC-specific type II deoxyribonucleases; D008274:Magnesium