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.
Research Article|February 15 1989
‘Star’ activity and complete loss of specificity of CeqI endonuclease
Biochem J (1989) 258 (1): 301-303.
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Z Izsvák, E Duda; ‘Star’ activity and complete loss of specificity of CeqI endonuclease. Biochem J 15 February 1989; 258 (1): 301–303. doi: https://doi.org/10.1042/bj2580301
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