A second type D restriction endonndease from Thermus aquaticus with an unusual sequence spedfldty

A Type II restriction endonuclease activity free of TaqI was prepared from Thermus Aquatious YT. The fraction contains two endonucleolytlo components with apparently different specificitiesi however the major activity is sufficiently dominant to allow partial digestion analysis of the position of recognition sites. A precise determination of the location of cleavage sites in pBR322 DNA and a computer-aided search for regions of homology in the vicinity of the cut sites indicate that this enzyme recognizes the nonpalindromic sequences GACCGA or CACCCA. Other related sequences are not cleaved, in particular, GACCCA and CACCGA, indicating that the enzyae requires the identity of nucleotides in the first and fifth positions, a type of specificity that has not been previously reported. The position of cleavage is located outside of the site and is represented as: w 5'-GACCGANNHNNNNNN NN-3' 3'-CTGGCTNNNNNNNNN NN-5 /\