An Isc-type extremely thermostable [2Fe-2S] ferredoxin from Aquifex aeolicus.: Biochemical, spectroscopic, and unfolding studies
An Isc-type extremely thermostable [2Fe-2S] ferredoxin from Aquifex aeolicus.: Biochemical, spectroscopic, and unfolding studies
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DOI：
10.1021/bi027116n
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发表时间：
2003-02-11
期刊：
影响因子：
2.9
通讯作者：
Meyer, J
中科院分区：
文献类型：
--
作者：
Mitou, G;Higgins, C;Meyer, J
对超嗜热细菌风产液菌（Aquifex aeolicus）的基因组的分析揭示了一个以前未检测到的基因的存在，该基因可能编码植物和植物型[2Fe-2S]铁氧还蛋白。该基因在大肠杆菌中的表达产生了一种新的热稳定的[2Fe-2S]铁氧还蛋白（命名为铁氧还蛋白5），其序列与参与铁-硫簇组装的铁氧还蛋白（Isc-Fd）的序列最相似。然而，它不同于后者的蛋白质具有缺失附近的N-和C-末端，没有半胱氨酸残基以外的参与[2Fe-2]簇协调。共振拉曼、低温MCD和EPR研究表明铁氧还蛋白5和棕色固氮菌Isc Fd具有相似的光谱。还原蛋白质的穆斯堡尔谱进行了分析与S = 1/2自旋哈密顿量和Bertrand和Gayda提出的配位场模型的框架下解释。A. aeolicus铁氧还蛋白5（-390 mV）与其与Isc-Fd的相关性一致。展开实验表明，A.风生菌铁氧还蛋白5是高度热稳定的（在pH 7时Tm = 106 ℃），尽管缺乏特征（例如，高含量的带电残基），通常与极端的热稳定性有关。已对超嗜热生物的测序基因组进行了植物型[2Fe-2S]铁氧化还原蛋白基因的测序。这两种蛋白质来自A. aeolicus中，表明这一广泛分布的蛋白质组在极端嗜热菌中几乎没有代表。
Analysis of the genome of the hyperthermophilic bacterium Aquifex aeolicus has revealed the presence of a previously undetected gene potentially encoding a plant- and mammalian-type [2Fe-2S] ferredoxin. Expression of that gene in Escherichia coli has yielded a novel thermostable [2Fe-2S] ferredoxin (designated ferredoxin 5) whose sequence is most similar to those of ferredoxins involved in the assembly of iron-sulfur clusters (Isc-Fd). It nevertheless differs from the latter proteins by having deletions near its N- and C-termini, and no cysteine residues other than those involved in [2Fe-2] cluster coordination. Resonance Raman, low-temperature MCD and EPR studies show close spectral similarities between ferredoxin 5 and the Isc-Fd from Azotobacter vinelandii. Mossbauer spectra of the reduced protein were analyzed with an S = 1/2 Spin Hamiltonian and interpreted in the framework of the ligand field model proposed by Bertrand and Gayda. The redox potential of A. aeolicus ferredoxin 5 (-390 mV) is in keeping with its relatedness to Isc-Fd. Unfolding experiments showed that A. aeolicus ferredoxin 5 is highly thermostable (T-m = 106 degreesC at pH 7), despite being devoid of features (e.g., high content of charged residues) usually associated with extreme thermal stability. Searches for genes potentially encoding plant-type [2Fe-2S] ferredoxins have been performed on the sequenced genomes of hyperthermophilic organisms. None other than the two proteins from A. aeolicus were retrieved, indicating that this otherwise widely distributed group of proteins is barely represented among hyperthermophiles.