Discovery of a novel ferredoxin from Azotobacter vinelandii containing two [4Fe-4S] clusters with widely differing and very negative reduction potentials
Discovery of a novel ferredoxin from Azotobacter vinelandii containing two [4Fe-4S] clusters with widely differing and very negative reduction potentials
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DOI：
10.1074/jbc.273.10.5514
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发表时间：
1998-03-06
影响因子：
4.8
通讯作者：
Burgess, BK
中科院分区：
文献类型：
--
作者：
Gao-Sheridan, HS;Pershad, HR;Burgess, BK
含有2个[4Fe-4S]（2+/+）簇的铁氧还蛋白可分为两类。“梭菌型”铁氧化还原蛋白具有两个Cys-Xaa-Xaa-Cys-Xaa-Xaa-Cys-Xaa-Xaa-Xaa-Cys-Pro基序。“染色质型”铁氧化还原蛋白具有一个该类型的基序和一个更不寻常的Cys-Xaa-Xaa-Cys-Xaa（7-9）-Cys-Xaa-Xaa-Xaa-Cys-Pro基序。在这里，我们报告了一种新的铁氧还蛋白（FdIII）的纯化棕色固氮菌，使12个小[Fe-S]蛋白，现在已经报道从这种生物体。前56个氨基酸残基的NH 2-末端测序表明FdIII是染色单体型铁氧还蛋白，与Chromatium vinosum铁氧还蛋白具有77%的同一性和88%的相似性。通过基质辅助激光解吸电离飞行时间质谱、铁分析、吸收、圆二色性和电子顺磁共振光谱对纯化的蛋白质的研究表明，FdIII在9，220-Da多肽中含有2个[4Fe-4S]（2+/+）簇。迄今为止已研究的所有2种[4Fe-4S]（2+/+）铁氧化还原蛋白，包括C. vinosum铁氧还蛋白，据报道对两个簇具有极其相似或相同的还原电位。相比之下，FdIII的电化学表征清楚地确定了两个[4Fe-4S]（2+/+）簇具有非常不同的和高度负的还原电位，与标准氢电极相比为-486 mV和-644 mV。
Ferredoxins that contain 2[4Fe-4S](2+/+) clusters can be divided into two classes. The "clostridial-type" ferredoxins have two Cys-Xaa-Xaa-Cys-Xaa-Xaa-Cys-Xaa-Xaa-Xaa-Cys-Pro motifs. The "chromatium-type" ferredoxins have one motif of that type and one more unusual Cys-Xaa-Xaa-Cys-Xaa(7-9)-Cys-Xaa-Xaa-Xaa-Cys-Pro motif. Here we report the purification of a novel ferredoxin (FdIII) from Azotobacter vinelandii which brings to 12 the number of small [Fe-S] proteins that have now been reported from this organism. NH2-terminal sequencing of the first 56 amino acid residues shows that FdIII is a chromatium-type ferredoxin with 77% identity and 88% similarity to Chromatium vinosum ferredoxin. Studies of the purified protein by matrix-assisted laser desorption ionization-time of flight mass spectroscopy, iron analysis, absorption, circular dichroism, and electron paramagnetic resonance spectroscopies show that FdIII contains 2[4Fe-4S](2+/+) clusters in a 9,220-Da polypeptide. All 2[4Fe-4S](2+/+) ferredoxins that have been studied to date, including C. vinosum ferredoxin, are reported to have extremely similar or identical reduction potentials for the two clusters. In contrast, electrochemical characterization of FdIII clearly establishes that the two [4Fe-4S](2+/+) clusters have very different and highly negative reduction potentials of -486 mV and -644 mV versus the standard hydrogen electrode.