Cloning and Nucleotide Sequenceof the Genes Encoding Restriction-Modification System from Acidophilic Bacterium Acidocella facilis 22M

The gene encoding the Afa22MI restriction-modification system recognizing the sequence 5'-CGATCG-3' was cloned from Acidocella facilis 22M and sequenced. The cloned DNA fragment contained three genes encoding the Afa22MI methylase (M.Afa22MI) , the putative restriction endonuclease Afa22MI (R.Afa22MI) and a very short patch repair endonuclease (Afa22MI vsr) . M. Afa22MI gene has the conserved motifs of C5-cytosine methyltransferase. Afa22MI vsr gene was localized upstream of M. Afa22MI gene in opposite orientation, and an open reading frame of R. Afa22MI has about 53% sequence similarity to the amino acid sequence for the variable region of M.XorⅡ. Afa22MI vsr has about 66% sequence similarity to the amino acid sequence of XorII vsr which was associated M. XorII.