Conformational and functional significance of the α140 side-chain in HbA:: a UV and visible resonance Raman study of three α140 mutants
Conformational and functional significance of the α140 side-chain in HbA:: a UV and visible resonance Raman study of three α140 mutants
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DOI：
10.1002/jrs.1322
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发表时间：
2005-04-01
影响因子：
2.5
通讯作者：
Friedman, JM
中科院分区：
文献类型：
--
作者：
Juszczak, L;Samuni, U;Friedman, JM
从成人血红蛋白(HBA)的三个α链突变体Yα140F、Yα140G和Yα140a的脱氧和CO衍生物中产生了连续波紫外共振拉曼(UVRR)和纳秒时间分辨可见共振拉曼光谱。UVRR结果表明，脱氧T态和连接R态的变构重要的α(1)β(2)界面都需要α140位上的芳香族侧链来实现野生型的三级构象。从脱氧衍生物的VRR谱中看到的v(Fe-His)，铁-近端组氨酸伸展模式的波数表明，即使当α(1)β(2)界面看起来是完整的时，α140酪氨酸和α93缬氨酸的羰基之间的氢键是获得与脱氧T态相关的完整四元约束所必需的。提出了一个模型，描述了与Wβ37和Yα140连接的一簇残基的堆积与a链血红素的近端应变/第四级约束程度之间的关系。在变构效应存在和不存在的情况下，三个突变体的CO衍生物的8 ns光产物的可见共振拉曼(VRR)光谱表明，三个突变体都可以进入R态，但它们对加入IHP的敏感性增强。在IHP存在下，Hb(Yα140F)突变体的CO衍生物表现出与用溶胶-凝胶矩阵分离的HBA非平衡群体和β37突变体的高亲和力T状态一致的性质，其中α(1)β(2)界面的铰链区被破坏。版权所有(C)2005 John Wiley&Sons，Ltd.
Continuous wave UV resonance Raman (UVRR) and nanosecond time-resolved visible resonance Raman spectra were generated from the deoxy and CO derivatives of three alpha-chain mutants of human adult hemoglobin (HbA): Y alpha 140F, Y alpha 140G and Y alpha 140A. The UVRR results show that an aromatic side-chain in the alpha 140 site is needed for achieving the wild-type tertiary conformation in the allosterically important alpha(1)beta(2) interface for both the deoxy T state and the liganded R state. The wavenumbers of v(Fe-His), the iron-proximal histidine stretching mode, seen in the VRR spectra from the deoxy derivatives show that the hydrogen bond between alpha 140 tyrosine and the carbonyl of alpha 93 valine is necessary to obtain the full quaternary constraint associated with the deoxy T state even when the alpha(1)beta(2) interface is seemingly intact. A model is presented that describes the relationship between the packing of a cluster of residues linked to both W beta 37 and Y alpha 140 and the extent of proximal strain/quaternary constraint at the a-chain heme. The visible resonance Raman (VRR) spectra of the 8 ns photoproduct of the CO derivatives of the three mutants in the presence and absence of allosteric effectors show that all three mutants can access the R state but they show enhanced sensitivity to added IHP. The CO derivative of the Hb(Y alpha 140F) mutant in the presence of IHP exhibits properties consistent with the high-affinity T state observed both for non-equilibrium populations of HbA isolated using sol-gel matrices and for beta 37 mutants where the hinge region of the alpha(1)beta(2) interface is disrupted. Copyright (c) 2005 John Wiley & Sons, Ltd.