Abstract: This invention provides restriction endonuclease Srf I, which is capable of recognizing the eight nucleotide base palindromic sequence shown below on a double stranded DNA molecule and cleaving the DNA chain at the asterisk-marked position resulting in blunt ends______________________________________ 5'GCCC*GGGC3' 3'CGGG*CCCG5' ______________________________________(wherein G and C respectively represent the nucleotides guanine and cytosine). The restriction endonuclease is produced by culturing Streptomyces rf in a culture medium and recovering it from the culture.The invention also provides polynucleotides encoding Srf I. Another aspect of this invention is to provide for the recombinant DNA production of Srf I. Another aspect of the invention is to provide for non-naturally occurring variants of Srf I, as well as the polynucleotides encoding these proteins.

Abstract: This invention provides restriction endonuclease, Srf I, capable of recognizing the eight nucleotide base palindromic sequence shown below on a double-stranded DNA molecule and cleaving the DNA chain at the asterisk-marked position resulting in blunt ends5' GCCC*GGGC 3'3' CGGG*CCCG 5'(wherein C and G respectively represent cytosine and guanine). The restriction endonuclease is produced by culturing Streptomyces rf in a culture medium and recovering it from the culture.