A NEW THERMOPHILIC STRAIN OF BACILLUS-COAGULANS PRODUCING SITE-SPECIFIC ENDONUCLEASE BCOKI

A thermophilic bacterial strain producing a new site-specific endonucl ease BcoKI was isolated from tobacco leaves. The phenotypic characteri zation of this strain, which was identified as a new strain of Bacillu s coagulans, is presented. BcoKI, a class-IIS restriction endonuclease , was obtained by three successive chromatographic procedures employin g blue agarose, hydroxyapatite, and heparin-Sepharose. BcoKI, an isosc hizomer of Ksp6321 [1], recognizes a hexanucleotide non-palindromic se quence 5'-CTCTTC-3' and cleaves this strand at a distance of one nucle otide from the 3'-cytosine and the opposite strand, four nucleotides f rom the 5'-guanine, to form a three-base-long single-strand 5'-overhan g.