Heme-bound tyrosine vibrations in hemoglobin M: Resonance Raman, crystallography, and DFT calculation
Heme-bound tyrosine vibrations in hemoglobin M: Resonance Raman, crystallography, and DFT calculation
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血红蛋白 M 中血红素结合的酪氨酸振动：共振拉曼、晶体学和 DFT 计算
DOI：
10.1016/j.bpj.2022.06.012
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发表时间：
2022
影响因子：
3.4
通讯作者：
Shibayama Naoya
中科院分区：
文献类型：
--
作者：
Nagatomo Shigenori;Shoji Mitsuo;Terada Takuto;Nakatani Kiyoharu;Shigeta Yasuteru;Hirota Shun;Yanagisawa Sachiko;Kubo Minoru;Kitagawa Teizo;Nagai Masako;Ohki Mio;Park Sam-Yong;Shibayama Naoya
血红蛋白M（Hemoglobins M，Hbs M）是人类血红蛋白的变体，其α或β亚基在α2β 2四聚体中含有一个铁血红素。虽然铁亚基不能结合O2，但它调节其对应的亚铁亚基的O2亲和力。我们研究了两种Hbs的共振拉曼光谱，M Iwate（α 87 His →酪氨酸[Tyr]）和M Boston（α 58 His → Tyr），分别在近端和远端位置以酪氨酸作为血红素轴向配体，它们在899和876 cm-1处表现出由三价铁（非二价铁）血红素产生的未归属共振拉曼谱带。我们用密度泛函理论对含对甲酚和/或4-甲基咪唑的铁卟啉模型进行了量子化学计算，结果表明未分配的谱带对应于Fe 3+结合的Tyr的呼吸样模式，并且对Fe-O-C（Tyr）角敏感。根据拉曼谱带的频率，预测了Hbs M Iwate和M Boston的Fe-O-C（Tyr）角分别为153.5°和129.2°。与此预测一致，X射线晶体学分析表明，在T四级结构中，Hbs M Iwate和M Boston的Fe-O-C（Tyr）角分别为153.6°和134.6°。它还显示了相似的Fe-O键长（1.96和1.97 π）和不同的倾斜角。
Hemoglobins M (Hbs M) are human hemoglobin variants in which either the α or β subunit contains a ferric heme in the α2β2tetramer. Though the ferric subunit cannot bind O2, it regulates O2affinity of its counterpart ferrous subunit. We have investigated resonance Raman spectra of two Hbs, M Iwate (α87His → tyrosine [Tyr]) and M Boston (α58His → Tyr), having tyrosine as a heme axial ligand at proximal and distal positions, respectively, that exhibit unassigned resonance Raman bands arising from ferric (not ferrous) hemes at 899 and 876 cm-1. Our quantum chemical calculations using density functional theory on Fe-porphyrin models withp-cresol and/or 4-methylimidazole showed that the unassigned bands correspond to the breathing-like modes of Fe3+-bound Tyr and are sensitive to the Fe-O-C(Tyr) angle. Based on the frequencies of the Raman bands, the Fe-O-C(Tyr) angles of Hbs M Iwate and M Boston were predicted to be 153.5° and 129.2°, respectively. Consistent with this prediction, x-ray crystallographic analysis showed that the Fe-O-C(Tyr) angles of Hbs M Iwate and M Boston in the T quaternary structure were 153.6° and 134.6°, respectively. It also showed a similar Fe-O bond length (1.96 and 1.97 Å) and different tilting angles.