A mutant UW 3, which is unable to fix N 2 in the presence of Mo (Nif -) but can undergo phenotypic reversal to Nif + under Mo_deficient conditions, was able to grow in Cr_containing but Mo_ and NH 3_deficient...A mutant UW 3, which is unable to fix N 2 in the presence of Mo (Nif -) but can undergo phenotypic reversal to Nif + under Mo_deficient conditions, was able to grow in Cr_containing but Mo_ and NH 3_deficient medium. A partly purified nitrogenase component Ⅰ protein obtained from UW 3 grown on the Cr_containing medium was shown to contain Fe and Cr (atom ratio of Fe to Cr and Mo to Cr: 11.60 and 0.41) and to have 70% of the C 2H 2_ and H +_reduction activity of MoFe protein from the wild_type strain of Azotobacter vinelandii Lipmann. The Cr_containing protein was different in subunit composition from that of MnFe protein purified from the mutant strain grown in the presence of Mn, but similar to that of MoFe protein, that is, it was a tetramer composed of two different subunits (α 2β 2). The preliminary results indicated that the Cr_containing protein might be a nitrogenase component Ⅰ protein.展开更多
文摘A mutant UW 3, which is unable to fix N 2 in the presence of Mo (Nif -) but can undergo phenotypic reversal to Nif + under Mo_deficient conditions, was able to grow in Cr_containing but Mo_ and NH 3_deficient medium. A partly purified nitrogenase component Ⅰ protein obtained from UW 3 grown on the Cr_containing medium was shown to contain Fe and Cr (atom ratio of Fe to Cr and Mo to Cr: 11.60 and 0.41) and to have 70% of the C 2H 2_ and H +_reduction activity of MoFe protein from the wild_type strain of Azotobacter vinelandii Lipmann. The Cr_containing protein was different in subunit composition from that of MnFe protein purified from the mutant strain grown in the presence of Mn, but similar to that of MoFe protein, that is, it was a tetramer composed of two different subunits (α 2β 2). The preliminary results indicated that the Cr_containing protein might be a nitrogenase component Ⅰ protein.
