摘要
A mutant UW 3, which is unable to fix N 2 in the presence of Mo (Nif -) but undergo phenotypic reversal to Nif + under Mo deficiency, was able to grow in Mo- and NH 3-deficient medium containing Mn, and the growth was accelerated by Mn at low concentration. A partly purified nitrogenase component Ⅰ protein separated from UW 3 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 C 2H 2- 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 Ⅰ protein.
棕色固氮菌 (AzotobactervinelandiiLipmann)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∶1.0 0 )并具有OPMoFe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。
基金
SupportedbytheNationalNaturalScienceFoundationofChina ( 2 97710 33)
