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.CGATCGを認識する Afa22MI 制限修飾系遺伝子を好酸性細菌 Acidocella facilis 22M より、クローニングし、塩基配列を決定した。その結果、C5-シトシンメチラーゼに特徴的なモチーフが保存された。M.Afa22MI 遺伝子、その上流に、M.Afa22MI 遺伝子とは逆方向に、 very short patch repair endonuclease 様タンパク質遺伝子（Afa22MI vsr）、制限酵素（R.Afa22MI）遺伝子と推定されるオープンリーディングフレームが見出された。M.Afa22MI の推定アミノ酸配列は、Xanthomonas oryzae pv. oryzae 由来 M.XorII の配列と全体で約63%、veriable region 内で約53%の高い配列類似性を示した。また、Afa22MI usr の推定アミノ酸配列も、M.XorIIに付随する XorII vsr の配列と約66%の高い類似性を示した