FeNO structure in distal pocket mutants of myoglobin based on resonance Raman spectroscopy
FeNO structure in distal pocket mutants of myoglobin based on resonance Raman spectroscopy
复制标题
基于共振拉曼光谱的肌红蛋白远端口袋突变体中的 FeNO 结构
DOI：
10.1021/bi026395b
复制
发表时间：
2003-05-06
期刊：
影响因子：
2.9
通讯作者：
Zgierski, MZ
中科院分区：
文献类型：
--
作者：
Coyle, CM;Vogel, KM;Zgierski, MZ
利用（15/14）NO加合物的同位素编辑共振拉曼光谱研究了一系列肌红蛋白突变体的FeNO振动频率，揭示了FeNO和NO的伸缩模式。后者产生的双峰带，作为费米共振与符合卟啉振动的结果，这些双峰进行了分析，通过曲线拟合，以获得nuNO频率。突变体之间nuNO的变化与相同突变体的CO加合物的nuCO变化相关。的相关性有一个接近统一的斜率，表示相等的灵敏度的NO和CO键的血红素口袋中的极性影响。一些突变体偏离的相关性，表明远端的相互作用不同的NO和CO加合物，可能是因为不同的远端残基的几何形状。与CO加合物中发现的强且一致的nuFeC/nuCO相关性相反，nuFeN仅与nuNO弱相关，并且相关性的斜率取决于哪个残基被突变。这种可变性被认为是由空间相互作用引起的，空间相互作用改变了FeNO的角度，从而改变了Fe-NO和N-O键级。这种效果是仿照密度泛函理论（DFT）和合理化的基础上的价异构体键合模型。自然弯曲的FeNO单元是比自然线性的FeCO单元更敏感的空间相互作用的报告者。一个重要的附加因素是键的强度，近端配体，它调节价异构体平衡。的FeNO单位是弯曲更强烈的MbNO比在无蛋白血红素-NO复合物，因为一个加强的近端键和远端的相互作用的组合。
FeNO vibrational frequencies were investigated for a series of myoglobin mutants using isotope-edited resonance Raman spectra of (15/14)NO adducts, which reveal the FeNO and NO stretching modes. The latter give rise to doublet bands, as a result of Fermi resonances with coincident porphyrin vibrations; these doublets were analyzed by curve-fitting to obtain the nuNO frequencies. Variations in nuNO among the mutants correlate with the reported nuCO variations for the CO adducts of the same mutants. The correlation has a slope near unity, indicating equal sensitivity of the NO and CO bonds to polar influences in the heme pocket. A few mutants deviate from the correlation, indicating that distal interactions differ for the NO and CO adducts, probably because of the differing distal residue geometries. In contrast to the strong and consistent nuFeC/nuCO correlation found for the CO adducts, nuFeN correlates only weakly with nuNO, and the slope of the correlation depends on which residue is being mutated. This variability is suggested to arise from steric interactions, which change the FeNO angle and therefore alter the Fe-NO and N-O bond orders. This effect is modeled with Density Functional Theory (DFT) and is rationalized on the basis of a valence isomer bonding model. The FeNO unit, which is naturally bent, is a more sensitive reporter of steric interactions than the FeCO unit, which is naturally linear. An important additional factor is the strength of the bond to the proximal ligand, which modulates the valence isomer equilibrium. The FeNO unit is bent more strongly in MbNO than in protein-free heme-NO complexes because of a combination of a strengthened proximal bond and distal interactions.