A mutant UW3, which is unable to fix N2 in the presence of Mo (Nif-) but undergo phenotypic reversal to Nif+ under Mo deficiency, was able to grow in Mo- and NH3-deficient medium containing Mn, and the growth was accelerated by Mn at low concentration. A partly purified nitrogenase component Ⅰ protein separated from UW3 grown in the Mn-containing medium was shown to contain Fe and Mn atoms (ratio of Fe/Mo/Mn: 10.41/0.19/1.00) with C2H2- and H+-reducing activity which almost equal to half of that of MoFe protein purified from wild-type mutant of Azotobacter vinelandii Lipmann. This protein was obviously different from MoFe protein in both absorption spectrum and circular dichroism, and the molecular weight of subunits in Mn-containing protein was close to that of α subunit in MoFe protein. The preliminary results indicated that the protein containing Mn might be a nitrogenase component Ⅰprotein.
含锰固氮酶组分I蛋白的纯化和特性
黄巨富 汪道涌 董志刚 汪志平 张华峰 吕玉兵 许祥明 赵颖
（中国科学院植物研究所，北京100093）
摘要：棕色固氮菌(Azotobacter vinelandii Lipmann)突变种UW3能在无Mo 而含Mn的无氨培养基中固氮生长.低浓度的Mn对UW3突变种生长有促进作用.从在Mn中生长的UW3菌体中分离得到的部分纯固氮酶组分Ⅰ蛋白含有Mn和Fe原子(Fe/Mo/Mn为10 .41∶0.19∶1.00)并具有OP MoFe蛋白一半的还原乙炔和质子的活性.这种蛋白的吸收光谱和圆二色谱与MoFe蛋白存在明显的差异,含Mn蛋白的亚基分子量都与 MoFe蛋白的α亚基相近.初步结果表明,这种含Mn蛋白可能是一种固氮酶组分Ⅰ蛋白.
关键词： 蛋白纯化；蛋白特性；含锰固氮酶蛋白；棕色固氮菌突变种uw3
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