MOSSBAUER STUDIES OF BEEF-HEART ACONITASE - EVIDENCE FOR FACILE INTERCONVERSIONS OF IRON-SULFUR CLUSTERS
MOSSBAUER STUDIES OF BEEF-HEART ACONITASE - EVIDENCE FOR FACILE INTERCONVERSIONS OF IRON-SULFUR CLUSTERS
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DOI：
10.1073/pnas.79.4.1096
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发表时间：
1982-01-01
期刊：
影响因子：
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通讯作者：
MUNCK, E
中科院分区：
文献类型：
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作者：
KENT, TA;DREYER, JL;MUNCK, E
用穆斯堡尔谱和电子顺磁共振谱对有氧条件下分离的牛心乌头酸酶进行了研究。在氧化状态下，酶在g = 2.01处显示EPR信号。穆斯堡尔谱数据表明，他的信号与3Fe团簇有关。在连二亚硫酸盐还原的顺乌头酸酶中，3Fe簇，可能是[3Fe-3S]型，处于整数电子自旋的顺磁状态（S = 2）;穆斯堡尔谱显示出具有3Fe簇的蛋白质的所有独特特征。在用Fe 2+活化乌头酸酶时，连二亚硫酸盐还原的顺磁性3Fe簇被转化为抗磁性（S = 0）形式。活化研究与Fe富集在57 Fe或56 Fe表明，活化转化成一个中心，有一个[4Fe-4S]核心的3Fe集群。这一结论是支持的观察，还原[4Fe-4S]集群的EPR信号特征，可以在适当的条件下引起。通常认为，用Fe 2+激活乌头酸酶会产生一个含有单一Fe 2+的活性位点。本文报道的数据表明，Fe 2+被用来重建[4Fe-4S]簇。
Beef heart aconitase, isolated under aerobic conditions, was studied with Mossbauer and EPR spectroscopy. In the oxidized state, the ezyme exhibits an EPR signal at g = 2.01. The Mossbauer data show that his signal is associated with a 3Fe cluster. In dithionite-reduced aconitase, the 3Fe cluster, probably of the [3Fe-3S] type, is in a paramagnetic state of integer electronic spin (S = 2); the Mossbauer spectra exhibit all the unique features reported for proteins with 3Fe clusters. On activation of aconitase with Fe2+, the paramagnetic 3Fe cluster of dithionite-reduced enzyme is converted into a diamagnetic (S = 0) form. Activation studies with Fe enriched in either 57Fe or 56Fe suggested that activation transforms the 3Fe cluster into a center that has a [4Fe-4S] core. This conclusion is supported by the observation that EPR signals characteristic of reduced [4Fe-4S] clusters can be elicited under appropriate conditions. It has frequently been assumed that the activation of aconitase with Fe2+ produces an active site containing a single Fe2+. The data reported here suggest that a Fe2+ is used to rebuild a [4Fe-4S] cluster.