NEW SITE-SPECIFIC ENDONUCLEASE AND METHYLASE FROM THE THERMOPHILIC STRAIN BACILLUS SPECIES KT6

The site-specific endonuclease R.BspKT6I and the cognate site-specific methylase M.BspKT6I were isolated to functionally pure state from the thermophilic strain Bacillus species KT6 by Sephadex G-100 gel filtra tion followed by chromatography on heparin-Sepharose and hydroxyapatit e. Endonuclease BspKT6I is not an isoschizomer, but an isomer of Sau3A I and MboI. It recognizes the GAT(down arrow)C sequence and cleaves it as shown by arrow, and, in distinction to Sau3AI and MboI, produces a protruding 3' dinucleotide. The cleavage of the site is inhibited by dam methylation. The sticky ends resulting from BspKT6I cleavage are i dentical and complementary to those formed after PvuI cleavage. The me thylase isolated from B. species KT6 protects the DNA from subsequent cleavage by BspKT6I. The methylated base is adenine.