Spectroscopic characterization of a novel tetranuclear Fe cluster in an iron-sulfur protein isolated from Desulfovibrio desulfuricans.
Spectroscopic characterization of a novel tetranuclear Fe cluster in an iron-sulfur protein isolated from Desulfovibrio desulfuricans.
复制标题
从脱硫弧菌脱硫菌中分离出的铁硫蛋白中新型四核 Fe 簇的光谱表征。
DOI：
10.1021/bi9723008
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Huynh,BH
中科院分区：
文献类型：
--
作者：
Tavares,P;Pereira,AS;Krebs,C;Ravi,N;Moura,JJ;Moura,I;Huynh,BH
穆斯堡尔谱和EPR谱用于表征从脱硫脱硫弧菌（ATCC 27774）分离的Fe−S蛋白中的Fe簇。这种蛋白质以前被认为含有六核Fe簇，但最近对从脱硫弧菌中分离的类似蛋白质的X射线晶体学测量表明，该蛋白质含有两个四核簇，一个立方烷型[4Fe−4S]簇和一个新结构的混合配体簇[Lindley et al.（1997）Abstract，Chemistry of Metals in Biological Systems，European Research Conference，托马尔，Portugal]。三种蛋白质样品平衡在不同的氧化还原电位（纯化，40和320 mV）进行了研究。在所有三个样品中，[4Fe−4S]簇被发现以抗磁性2+氧化态存在，并显示出典型的穆斯堡尔谱。发现该新颖结构的簇具有氧化还原活性。在320-mV和纯化的样品中，簇处于其完全氧化和单电子还原状态之间的氧化还原平衡。在40-mV样品中，团簇处于双电子还原状态。不同的光谱成分与簇2中的三种氧化态的四个Fe位点进行了鉴定。的Fe网站得到的光谱参数反映不同的配体环境，使其能够分配到个人的Fe网站的光谱成分。在完全氧化状态下，所有四个铁离子都是高自旋铁离子，并且反铁磁耦合形成抗磁性S = 0状态。在一个电子和两个电子的还原态，还原电子被发现本地化，连续，到两个Fe网站，是丰富的氧/氮配体。基于X射线结构和穆斯堡尔参数，可以尝试识别还原的Fe位点。EPR和穆斯堡尔谱数据表明，双电子团簇是顺磁性的，具有非零的整数自旋。对于单电子约化的团簇，数据表明自旋为9/2的半整数。特征罚款和超精细参数的所有四个Fe网站。结构的影响和自旋耦合相互作用的性质进行了讨论。
Mössbauer and EPR spectroscopies were used to characterize the Fe clusters in an Fe−S protein isolated fromDesulfovibrio desulfuricans(ATCC 27774). This protein was previously thought to contain hexanuclear Fe clusters, but a recent X-ray crystallographic measurement on a similar protein isolated fromDesulfovibrio vulgarisshowed that the protein contains two tetranuclear clusters, a cubane-type [4Fe−4S] cluster and a mixed-ligand cluster of novel structure [Lindley et al. (1997) Abstract, Chemistry of Metals in Biological Systems, European Research Conference, Tomar, Portugal]. Three protein samples poised at different redox potentials (as-purified, 40 and 320 mV) were investigated. In all three samples, the [4Fe−4S] cluster was found to be present in the diamagnetic 2+ oxidation state and exhibited typical Mössbauer spectra. The novel-structure cluster was found to be redox active. In the 320-mV and as-purified samples, the cluster is at a redox equilibrium between its fully oxidized and one-electron reduced states. In the 40-mV sample, the cluster is in a two-electron reduced state. Distinct spectral components associated with the four Fe sites of cluster 2 in the three oxidation states were identified. The spectroscopic parameters obtained for the Fe sites reflect different ligand environments, making it possible to assign the spectral components to individual Fe sites. In the fully oxidized state, all four iron ions are high-spin ferric and antiferromagnetically coupled to form a diamagneticS= 0 state. In the one-electron and two-electron reduced states, the reducing electrons were found to localize, consecutively, onto two Fe sites that are rich in oxygen/nitrogen ligands. Based on the X-ray structure and the Mössbauer parameters, attempts could be made to identify the reduced Fe sites. For the two-electron reduced cluster, EPR and Mössbauer data indicate that the cluster is paramagnetic with a nonzero interger spin. For the one-electron reduced cluster, the data suggest a half-integer spin of9/2. Characteristic fine and hyperfine parameters for all four Fe sites were obtained. Structural implications and the nature of the spin-coupling interactions are discussed.