Cardenas J, Mortenson L E
J Bacteriol. 1975 Sep;123(3):978-84. doi: 10.1128/jb.123.3.978-984.1975.
The role of Mo in the activity and synthesis of the nitrogenase components of Clostridium pasteurianum has been studied by observing the competition of Mo with its structural analogue W. Clostridial cells when fixing N2 appeared strictly dependent upon the available Mo, showing maximal N2-fixing activity at molybdate concentrations in the media of 10 muM. Cells grown in media with 3 times 10(-6) muM Mo, although showing good growth, had only 15% as much N2-fixing activity. In the presence of W the synthesis of both nitrogenase components, molybdoferredoxin and azoferredoxin, was affected. Attempts to produce nitrogenase in W-grown cells by addition of high molybdenum to the media in the presence of inhibitors of protein synthesis showed that Mo incorporation into a possible inactive preformed apoenzyme did not occur. Unlike other molybdoenzyme-containing cells, in which W either is incorporated in place of Mo to yield inactive protein or initiates the production of apoprotein, C. pasteurianum forms neither a tungsten substituted molybdoferredoxin nor an apoprotein. It is concluded that in C. pasteurianum molybdenum is an essential requirement for both the biosynthesis and activity of its nitrogenase.
通过观察钼与其结构类似物钨之间的竞争，研究了钼在巴氏芽孢杆菌固氮酶组分活性和合成中的作用。巴氏芽孢杆菌在固定氮气时，其细胞表现出对可利用钼的严格依赖性，在培养基中钼酸盐浓度为10μM时显示出最大固氮活性。在含3×10⁻⁶μM钼的培养基中生长的细胞，尽管生长良好，但固氮活性仅为15%。在有钨存在的情况下，固氮酶的两个组分，即钼铁蛋白和固氮铁蛋白的合成均受到影响。在蛋白质合成抑制剂存在的情况下，通过向在钨培养基中生长的细胞添加高浓度钼来尝试产生固氮酶，结果表明钼并未掺入可能无活性的预先形成的脱辅基酶中。与其他含钼酶的细胞不同，在其他细胞中钨要么取代钼以产生无活性的蛋白质，要么引发脱辅基蛋白的产生，而巴氏芽孢杆菌既不形成钨取代的钼铁蛋白，也不形成脱辅基蛋白。得出的结论是，在巴氏芽孢杆菌中，钼是其固氮酶生物合成和活性的必需条件。
