Heme structures of five variants of hemoglobin M probed by resonance Raman spectroscopy.
Heme structures of five variants of hemoglobin M probed by resonance Raman spectroscopy.
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DOI：
10.1021/bi036170g
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发表时间：
2004-06
期刊：
影响因子：
2.9
通讯作者：
Yayoi Jin;M. Nagai;Y. Nagai;S. Nagatomo;T. Kitagawa
中科院分区：
文献类型：
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作者：
Yayoi Jin;M. Nagai;Y. Nagai;S. Nagatomo;T. Kitagawa
α-异常血红蛋白（Hb）M变体显示出不同于β-异常Hb M变体的生理特性，即正常亚基的极低的氧亲和力和对异常甲硫氨酸亚基的酶还原和化学还原的非凡抗性。为了深入了解血红素结构对Hb M的这些差异的贡献，我们检测了5种Hb M在1700至200 cm（-1）频率范围内的406.7 nm激发共振拉曼（RR）光谱。在高频区域，对于面内骨架模式（nu（C=C）、nu（37）、nu（2）、nu（11）和nu（38）带），观察到met-alpha和met-beta异常亚基之间的显著差异，这可能反映了由于酪氨酸配位引起的血红素铁的面外位移引起的血红素结构的不同扭曲。在900 cm（-1）以下，Hb M Iwate [alpha（F8）His --> Tyr]与Hb M Boston [alpha（E7）His --> Tyr]相比，表现出不同的nu（15）、gamma（11）、delta（C（beta）C（a）C（B））（2，4）和delta（C（beta）C（c）C（d））（6，7）光谱模式，尽管两种血红素都与Tyr配位。β异常Hb M变体，即Hb M Hyde Park [β（F8）His --> Tyr]、Hb M萨斯卡通[β（E7）His --> Tyr]和Hb M密尔沃基[β（E11）瓦尔--> Glu]，显示出与metHb A相似的RR带型，但存在一些微小的个体差异。Hb M’s的高铁亚基特征性RR带经化学还原完全消失，异常亚基的亚铁血红素不再与Tyr或Glu结合。它们与远端（E7）或近端（F8）His结合，这通过在441.6 nm激发RR光谱中215 cm（-1）处存在nu（Fe-His）模式得到证实。一个可能的参与血红素畸变的异常亚基的还原性和正常亚基的氧亲和力的差异进行了讨论。
The alpha-abnormal hemoglobin (Hb) M variants show physiological properties different from the beta-abnormal Hb M variants, that is, extremely low oxygen affinity of the normal subunit and extraordinary resistance to both enzymatic and chemical reduction of the abnormal met-subunit. To get insight into the contribution of heme structures to these differences among Hb M's, we examined the 406.7-nm excited resonance Raman (RR) spectra of five Hb M's in the frequency region from 1700 to 200 cm(-1). In the high-frequency region, profound differences between met-alpha and met-beta abnormal subunits were observed for the in-plane skeletal modes (the nu(C=C), nu(37), nu(2), nu(11), and nu(38) bands), probably reflecting different distortions of heme structure caused by the out-of-plane displacement of the heme iron due to tyrosine coordination. Below 900 cm(-1), Hb M Iwate [alpha(F8)His --> Tyr] exhibited a distinct spectral pattern for nu(15), gamma(11), delta(C(beta)C(a)C(b))(2,4), and delta(C(beta)C(c)C(d))(6,7) compared to that of Hb M Boston [alpha(E7)His --> Tyr], although both heme irons are coordinated by Tyr. The beta-abnormal Hb M variants, namely, Hb M Hyde Park [beta(F8)His --> Tyr], Hb M Saskatoon [beta(E7)His --> Tyr], and Hb M Milwaukee [beta(E11)Val --> Glu], displayed RR band patterns similar to that of metHb A, but with some minor individual differences. The RR bands characteristic of the met-subunits of Hb M's totally disappeared by chemical reduction, and the ferrous heme of abnormal subunits was no longer bonded with Tyr or Glu. They were bonded to the distal (E7) or proximal (F8) His, and this was confirmed by the presence of the nu(Fe-His) mode at 215 cm(-1) in the 441.6-nm excited RR spectra. A possible involvement of heme distortion in differences of reducibility of abnormal subunits and oxygen affinity of normal subunits is discussed.