Site-Specific Endonuclease from Thermophilic Bacillus Species MK Strain is Isoschizomers of SalI

M. A. Kerzhner,¹ S. A. Shiryaev,¹ L. A. Zheleznaya,² and N. I. Matvienko^1,3

¹Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142292 Russia; fax: (095) 924-0493; E-mail: protres@sovam.com

²Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142292 Russia; fax: (095) 135-6219.

³To whom correspondence should be addressed.

Submitted February 25, 1997; revision submitted April 3, 1997.

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Screening of thermophilic bacterial strains revealed a strain containing site-specific endonuclease BspMKI. This endonuclease was purified to functional homogeneity during sequential chromatographic steps. The enzyme recognizes sequence 5´-G^vTCGAC-3´ on DNA molecule and is isoschizomer of endonuclease SalI. The molecular mass of BspMKI is about 45 kD. The enzyme is maximally active at 55°C and MRB (50 mM NaCl, 10 mM Tris-HCl, pH 7.4, 10 mM MgCl₂, 1 mM dithiothreitol) is the optimal buffer. The enzyme is highly stable and retains its activity during two weeks at room temperature.

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KEY WORDS: site-specific endonuclease, isoschizomer, restriction, sequencing.

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