Resonance Raman study of the .mu.-oxo-bridged binuclear iron center in oxyhemerythrin
Resonance Raman study of the .mu.-oxo-bridged binuclear iron center in oxyhemerythrin
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氧血红蛋白中μ-氧桥双核铁中心的共振拉曼研究
DOI：
10.1021/ja00329a054
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发表时间：
1984
影响因子：
15
通讯作者：
J. Sanders
中科院分区：
文献类型：
--
作者：
A. K. Shiemke;T. Loehr;J. Sanders
利用共振拉曼光谱技术研究了海洋管藻Phascolopsis gouldii的呼吸蛋白--二氯氰菊酯。在紫外光激发下，在486 cm~(-1)处发现了VS(Fe-0-Fe)，从而确定了氯氰菊酯中u-氧桥联双核铁中心的存在。在H_2180溶剂中，486-cm~(-1)振动模移至=475 cm~(-1)，与其他u-氧桥联Fe(III)蛋白，如几种甲基氰菊酯和核糖核苷酸还原酶的变化幅度相似。对含氧氯菊酯中^(Fe-O-Fe)模的增强谱的研究表明，共振是通过耦合到=360 nm跃迁而发生的，并将该带归属为O2‘Fe(III)电荷转移过程。相比之下，叠氮甲烷红蛋白在507 cm~(-1)处的VS(Fe-O-Fe)模在紫外光下也有很强的增强作用，但在可见光激发下可以观察到这种模式。它的增强轮廓很复杂，在=525、430和<；350 nm处显示出明显的最大值。这些数据表明，这两个发色团的电子结构存在显著差异。本研究的进一步新发现是观察到氧化菊酯的=753 cm~(-1)和叠氮甲基菊酯的=768 cm~(-1)处的谱线，这些谱线归属于Fe-O-Fe桥原子的不对称振动。这些频率在H_2180中也经历了=35厘米~(-1)的同位素位移以降低能量，正如模型络合物所预期的那样，其中红外活性^(Fe-O-Fe)已经被很好地记录下来。此外，在叠氮甲基红色素中还发现了Fe-O-Fe的变形，在H_2SO和H_2180中分别出现在292 cm~(-1)和286 cm~(-1)处。这些新数据为金属蛋白中这一结构单元的共振拉曼光谱表征提供了坚实的基础。我们还研究了D20的溶剂效应，而叠氮甲基菊酯没有显示出对重离子敏感的振动模式，氧代菊酯中位于844 cm“1的v(OO)和位于503 cm”1的v(Fe-02)在D20中分别移动了+4和-3 cm-1。由于氚的同位素效应似乎是氯氰菊酯所特有的，所以结合的过氧化氢很可能是质子化的。过氧化氢部分与氧桥氧发生内部氢键作用的能力可能是造成氯化菊酯电子结构区别于甲基氯菊酯和连接的甲基氯菊酯的关键。氯化菊酯是几种海洋脊椎动物的呼吸蛋白。杂氯氰菊酯的氧结合部位含有两个非血红素铁，它们可逆地结合一个二氧化氧分子。1‘3蛋白质的脱氧形式含有八面体配位的高自旋Fe(II)。2‘4与氧结合时，电荷从两个铁转移到氧，得到过氧化物络合物(Fe1)2-022“。光谱研究表明，这两个铁都是高自旋的Fe(III)，具有有效的八面体
Oxyhemerythrin, the respiratory protein of the marine sipunculid Phascolopsis gouldii, was investigated by resonance Raman spectroscopy. The presence of a u-oxo-bridged binuclear iron center in oxyhemerythrin was established by finding vs (Fe-0-Fe) at 486 cm'1 with ultraviolet excitation. In H2180 solvent, the 486-cm" 1 vibrational mode shifts to= 475 cm'1, a shift similar in magnitude to that observed for other u-oxo-bridged Fe (III) proteins, such as several methemerythrins and ribonucleotide reductase. A study of the enhancement profile of the^(Fe-O-Fe) mode in oxyhemerythrin indicatesthat resonance occurs by coupling to the= 360-nm transition and serves to assign this band to an O2' Fe (III) charge-transfer process. By contrast, although the vs (Fe-O-Fe) mode in azidomethemerythrin at 507 cm'1 is also strongly enhanced in the UV, this mode is observable with visible-light excitation. Its enhancement profile is complex, showing apparent maxima at= 525, 430, and< 350 nm. These data indicate that significant differences exist in the electronic structures of the two chromophores. Further new findings in the present study are the observation of spectral lines at= 753 cm" 1 in oxyhemerythrin and 768 cm'1 in azidomethemerythrin that are assigned to the asymmetricvibration of the Fe-O-Fe bridge atoms. These frequencies also undergo isotope shifts in H2180 by= 35 cm'1 to lower energy, as expected from modelcomplexes where the infrared active^(Fe-O-Fe) have been well documented. In addition, the Fe-O-Fe deformation has been identified in azidomethemerythrin where it occurs at 292 cm" 1 in H2lsO and 286 cm" 1 in H2180. The new data provide a firm ground for the resonance Raman spectroscopic characterizationof this structural unit in metalloproteins. D20 solvent effects were also investigated; whereas azidomethemerythrin shows no deuterium-sensitive vibrational modes, both v (OO) at 844 cm" 1 and v (Fe-02) at 503 cm" 1 in oxyhemerythrin were seen to shift in D20 by+ 4 and-3 cm-1, respectively. Since the deuterium isotope effect appears to be specific for oxyhemerythrin, it is likely that the bound peroxide is protonated. The ability of the hydroperoxide moiety to undergo internal hydrogen bonding with theu-oxo bridge oxygen may be the key to electronic structural differences in oxyhemerythrin relative to methemerythrin and ligated methemerythrins.Hemerythrin is the respiratory protein of several marinein-vertebrates. The oxygen binding site of hemerythrin contains two non-heme irons which reversibly bind one molecule of dioxygen. 1'3 The deoxy formof the protein contains high-spin Fe (II) with octahedral coordination. 2'4 Upon binding dioxygen, charge is transferred from both irons to the dioxygen to give a peroxide complex,(Fenl) 2-022". This representation of the active site of oxyhemerythrin is supported by spectroscopic studies which have shown both irons to be high-spin Fe (III) witheffectively octahedral