A NEW SITE-SPECIFIC ENDONUCLEASE BSPKT5I

A new site-specific endonuclease (BspKT5I) has been isolated from the thermophilic soil bacterium Bacillus KT5 by chromatography on Blue aga rose, hydroxyapatite, and heparin-Sepharose;it is free from interferin g impurities. On double-stranded DNA, BspKT5I recognizes the sequence 5'-CTGAAG16N down arrow/3'-GACTTC14N up arrow and cleaves the DNA at t he recognition site indicated by the arrows to form 3ii-protruding din ucleotide termini. The isolated endonuclease is an isoschizomer of Eco 57I. However, unlike Eco57I, it is not stimulated by S-adenosylmethion ine (SAM) and thus belongs to subclass IIS and not to class IV, as Eco 57I. Furthermore, endonuclease BspKT5I, in contrast to Eco57I, has no methylase activity.