SruI restriction endonuclease from Selenomonas ruminantium.

SruI, specific restriction endonuclease, has been characterized from Selenomonas ruminantium isolated from the rumen of fallow deer. Results from the study demonstrate that S. ruminantium 18D possesses a type II restriction endonuclease, which recognizes the sequence 5'-TTT decreases AAA-3'. The recognition sequence of SruI was identified using digestions on pBR322, pBR328, pUC18, M13mp18RF, pACYC184 and lambda DNA. The cleavage patterns obtained were compared with computer-derived data. SruI recognises the palindromic hexanucleotide sequence and cleaves DNA after the third T in the sequence, producing blunt ends. The purification and characterization of restriction endonuclease SruI presented here is the first described for Selenomonas ruminantium spp. and demonstrates that this microorganism possesses a DNA-cleaving enzyme with the same specificity as DraI or AhaIII.