(The) purification and characterization of Zan Ⅰ endonuclease from zymomonas.anaerobia

Abstract

A new sequence specific endonuclease, Zan I has been purified from Zymomonas anaerobia (NCI B8227). The purified protein was homogeneous as judged by 10\% polyacrylamide gel electrophoresis in the presence of 0.1\% SDS, and the subunit molecular weight was $30,000 \pm 1,000$ daltons. For the purification of the enzyme, 300 g of cells (wet weight) were used and broken by French Press at 20,000P.S.I. After ammonium sulfate fractionation, the enzyme was further purified by phospho cellulose column chromatography, DEAE cellulose column chromatography, Hydroxyl-apatite column chromatography and phospho cellulose column chromatography. From the dideoxy sequencing it was demonstrated that the new enzyme Zan I endonuclease (an isoschizomer of Eco RII, Bst NI, etc.), recognizs 5``-CC$^{\downarrow{A}}_T$GG-3`` and cleaves at the site indicated by the arrows. Also Zan I endonuclease was able to cleave dom-methylated DNA which is resistant to the digestion with Eco RII endonuclease. In order to study the catalytic properties of Zan I endonuclease, ($^3$H)-labeled lambda DNA was used as a substrate. The enzyme showed maximum activity at pH values between 7.0 and 9.0 in the presence of 10 mM MgCl$_2$, 10 mM NaCl. The optimum temperature for Zan I endonuclease activity is $42\,^\circ\!C$, which is different from Bst NI endonuclease. Also the enzyme activity was not changed in the presence of 150 mM NaCl.