Effect of magnesium adenosine 5'-triphosphate on the accessibility of the iron of clostridial azoferredoxin, a component of nitrogenase.
Effect of magnesium adenosine 5'-triphosphate on the accessibility of the iron of clostridial azoferredoxin, a component of nitrogenase.
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5-三磷酸腺苷镁对梭菌偶氮铁氧化还原蛋白（固氮酶的一种成分）的铁可及性的影响。
DOI：
10.1021/bi00708a023
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发表时间：
1974
期刊：
影响因子：
2.9
通讯作者：
L. Mortenson
中科院分区：
文献类型：
--
作者：
G. Walker;L. Mortenson
古斯塔夫斯A.步行者和伦纳德E. Mortenson* 摘要：偶氮铁氧还蛋白至少有三种不同的相互转化状态：氧化态（其活性不被破坏）、还原态和在镁ATP存在下的还原态。这些状态中的每一个都可以在固氮酶催化的还原中起作用。仅当偶氮铁氧还蛋白与镁ATP络合时，通过1，2 ′-联吡啶从偶氮铁氧还蛋白中快速去除铁与还原的偶氮铁氧还蛋白-镁ATP状态的电子顺磁共振谱中的损失直接相关。在不存在α，α ′-联吡啶的情况下，镁ATP的作用是可逆的。ATP镁的作用是高度特异性的，因为没有其他检测的镁核苷酸催化铁从偶氮铁氧化还原酶快速转移到a，o：′-联吡啶。此外，另一种固氮酶组分铁氧还蛋白的铁在加入L后不能被1，1-联吡啶接近，在固氮酶将电子从还原剂催化转移到二氮时需要LTP水解（Mc-Nary和Burris，1962; Mortenson，1964;哈代和D 'Eustachio，1964）。该酶的组分偶氮铁氧还蛋白（铁蛋白）或铁氧还蛋白（铼铁蛋白）在另一种不存在时都没有酶活性（Mortenson et al.，1967年）。虽然已经提出了几种假说，但还不清楚ATP在固氮酶还原底物中的作用。其中有：（1）ATP激活电子（Mortenson，1964;哈代et al.，1965），（2）ATP介导的电子转移（Mortenson，1964;哈代and Burns，1968），（3）ATP支持的底物结合（Kelly and Lang，1970），和（4）ATP诱导的一种或两种构象的变化
Gustavus A. Walker and Leonard E. Mortenson* abstract: Azoferredoxin has been shown to have a minimum of three different interconvertible states: an oxidized state (one in which its activity is not destroyed), a reduced state, and a reduced state in the presence of magnesium ATP. Each of these states could function in the reductions catalyzed by nitrogenase. The rapid removal of iron from azoferredoxin by,'-dipyridyl, only when azoferredoxin is complexed with magnesium ATP, is directly correlated with a loss in the electron paramagnetic resonance spectrum of the reduced azo-ferredoxin-magnesium ATP state. In the absence of a, a'-dipyridyl, the effect of magnesium ATP is reversible. The magnesium ATP effect is highly specific since no other magnesium nucleotide examined catalyzed the rapid transfer of iron from azoferredoxinto a, o:'-dipyridyl. In addition, the iron of molybdoferredoxin, the other nitrogenase component, is not made accessible to,'-dipyridyl upon addition ofL JLTP hydrolysis is required in the catalytic transfer of electrons by nitrogenase from a reductant to dinitrogen (Mc-Nary and Burris, 1962; Mortenson, 1964; Hardy and D’Eustachio, 1964). Neither component of theenzyme, azoferredoxin (iron-protein) or molybdoferredoxin (molybdenum-iron protein), is enzymatically active in the absence of the other (Mortenson et al., 1967). It is not understood how ATP functions in the reduction of substrates by nitrogenase, although several hypotheses have been advanced. Among these postu-lates are:(1) electron activation by ATP (Mortenson, 1964; Hardy et al., 1965),(2) ATP mediated electron transfer (Mortenson, 1964; Hardy and Burns, 1968),(3) ATP sup-ported substrate binding (Kelly and Lang, 1970), and (4) ATP induced changes in the conformation of one or both