Verhagen M F, Voorhorst W G, Kolkman J A, Wolbert R B, Hagen W R
Department of Biochemistry, Agricultural University, Wageningen, The Netherlands.
FEBS Lett. 1993 Dec 20;336(1):13-8. doi: 10.1016/0014-5793(93)81599-u.
Desulfoferrodoxin from Desulfovibrio vulgaris, strain Hildenborough, is a homodimer of 28 kDa; it contains two Fe atoms per 14.0 kDa subunit. The N-terminal amino-acid sequence is homogeneous and corresponds to the previously described Rho gene, which encodes a highly charged 14 kDa polypeptide without a leader sequence. Although one of the two iron centers, FeA, has previously been described as a 'strained rubredoxin-like' site, EPR of the ferric form proves very similar to that of the pentagonal bipyramidally coordinated iron in ferric complexes of DTPA, diethylenetriaminepentaacetic acid: both systems have spin S = 5/2 and rhombicity E/D = 0.08. Unlike the Fe site in rubredoxin the FeA site in desulfoferrodoxin has a pH dependent midpoint potential with pKox = 9.2 and pKred = 5.3. Upon reduction (Em,7.5 = +2 mV) FeA exhibits an unusually sharp S = 2 resonance in parallel-mode EPR. The second iron, FeB, has S = 5/2 and E/D = 0.33; upon reduction (Em,7.5 = +90 mV) FeB turns EPR-silent.
来自希登伯勒脱硫弧菌（Desulfovibrio vulgaris, strain Hildenborough）的脱硫铁氧化还原蛋白是一种28 kDa的同型二聚体；每个14.0 kDa亚基含有两个铁原子。其N端氨基酸序列是一致的，与先前描述的Rho基因相对应，该基因编码一种不带前导序列的高电荷14 kDa多肽。虽然两个铁中心之一的FeA先前被描述为“类扭曲红素铁氧化还原蛋白”位点，但三价铁形式的电子顺磁共振（EPR）结果证明与二乙烯三胺五乙酸（DTPA）三价铁配合物中五角双锥配位铁的EPR非常相似：这两个体系的自旋S = 5/2，菱形度E/D = 0.08。与红素铁氧化还原蛋白中的铁位点不同，脱硫铁氧化还原蛋白中的FeA位点具有pH依赖性中点电位，pKox = 9.2，pKred = 5.3。还原后（Em,7.5 = +2 mV），FeA在平行模式EPR中表现出异常尖锐的S = 2共振。第二个铁原子FeB，S = 5/2，E/D = 0.33；还原后（Em,7.5 = +90 mV），FeB的EPR信号消失。
