title: 'Star' activity and complete loss of specificity of CeqI endonuclease.
abstract: Restriction endonuclease CeqI, an isoschizomer of EcoRV, exhibits 'star' activity, a relaxation of specificity in the presence of Mn2+, dimethyl sulphoxide or glycerol. The enzyme cleaves a set of sequences that differ from the canonical GATATC by only one nucleotide in positions 2, 3, 4 or 5. Two of these sequences are not cleaved if modified by dam methylase. A further loss of specificity can be observed in circumstances less favourable for the enzyme, namely low-ionic-strength buffers of pH values below 6.0 or above 9.4. This activity seems to cleave DNA at any sequence, producing a smear instead of well-defined bands. Partial renaturation of the denatured enzyme gives rise to a similar non-specific nuclease activity.
authors.affiliation: Institute of Biochemistry, Hungarian Academy of Sciences, Szeged.
authors.forename: Z
authors.initials: Z
authors.lastname: Izsvák
authors.forename: E
authors.initials: E
authors.lastname: Duda
mesh_terms: D001483:Base Sequence; D004262:DNA Restriction Enzymes / Q000235:genetics*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005990:Glycerol / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008345:Manganese / Q000494:pharmacology; D012240:Rhodococcus
chemical_list: D008345:Manganese; D004262:DNA Restriction Enzymes; D015252:Deoxyribonucleases, Type II Site-Specific; C027440:GATATC-specific type II deoxyribonucleases; D005990:Glycerol; D004121:Dimethyl Sulfoxide