SITE-SPECIFIC ENDONUCLEASE ABAI FROM AZOSPIRILLUM-BRASILENSE UQ-1796 IS AN ISOSCHIZOMER OF ENDONUCLEASE BCLI

The site-specific endonuclease AbaI was isolated and purified to funct ional purity from the soil nitrogen-fixing bacterium Azospirillum bras ilense UQ 1796. Purification included successive chromatography on col umns with phosphocellulose, heparin-Sepharose, and hydroxyapatite. The purified enzyme recognizes the palindromic DNA sequence 5'-T(down arr ow)ATCA-3' and cleaves it as shown by the arrow. The isolated enzyme b elongs to class II restriction endonucleases and is an isoschizomer of endonuclease BclI. The enzyme AbaI is active at 26-56 degrees C. The optimal temperature is 48 degrees C and the optimal buffer is LRB.