Site-specific endonuclease from thermophilic Bacillus species MK strain is isoschizomer of SalI

Screening of thermophilic bacterial strains reveal ed a strain containing site-specific endonuclease BspMK1. This endonuclease was purified to functional homogeneity during sequential chromatographic steps. The enzyme recognizes sequence 5'-G down arrow TCGAC-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 degrees C and MRB (50 mM NaCl, 10 mM Tris-HCl, pH 7.4, IO mM MgCl2, 1 mM dithiothreitol) is the optimal buffer. The enzyme is highly stable and retains its activity during two weeks at room temperature.