[A new site-specific endonuclease and methylase from a thermophilic strain of Bacillus species KT6].

The site-specific endonuclease R.BspKT6I and the cognate site-specific methylase M.BspKT6I have been isolated from the thermophilic strain of Bacillus species KT6 using gel-filtration on Sephadex G100 followed by chromatography on heparin-Sepharose and hydroxyapatite. Endonuclease BspKT6I is an isomer but not an isoschizomer of Sau3AI and MboI. It recognized on the DNA molecule the GAT decreases C sequence and cleaves it; however, unlike Sau3AI and MboI it produces 3'-protruding dinucleotides. The site cleavage is inhibited by dam-methylation. The sticky ends resulting from the BspKT6I cleavage are identical and complementary to the ends formed after the PvuI cleavage. The isolated from the B. species KT6 methylase protects the DNA from subsequent cleavage by BspKT6I. Adenine is a methylated base.