A photolysis-triggered heme ligand switch in H93G myoglobin
A photolysis-triggered heme ligand switch in H93G myoglobin
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DOI：
10.1021/bi0023403
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发表时间：
2001-05-01
期刊：
影响因子：
2.9
通讯作者：
Boxer, SG
中科院分区：
文献类型：
--
作者：
Franzen, S;Bailey, J;Boxer, SG
利用共振拉曼光谱和步进扫描傅里叶变换红外光谱(FTIR)研究了肌红蛋白H93G近腔突变体在近侧不存在外源配体的情况下，亚铁血红素铁的结合状态。肌红蛋白H93G突变体的制备已经被报道用于血红素铁的各种轴向配体(例如取代的吡啶和咪唑)[DePillis，G.，Decatur，S.M，Barrick，D.和Boxer，S.G.(1994)J.Am化学。SoC。116、6981-6982]。本研究检测了不含外源配体的H93G肌红蛋白制剂中血红素的连接状态。在脱氧形式的H93G中，共振拉曼光谱证据表明水是脱氧血红素铁的轴向(第五)配体。对CO加合物的红外C-O和拉曼Fe-C伸缩频率的分析表明，它与组氨酸反式配体为六配位。在CO光解后，步进扫描FTIR和饱和共振拉曼光谱都显示出连接的时间依赖性变化，从而得出了H93G蛋白中存在构象驱动的配体开关的结论。在没有外源含氮配体的情况下，CO反式作用稳定了内源性组氨酸连接，而构象菌株有利于CO光解后组氨酸的解离。五配位络合物中的组氨酸被水取代估计发生在
Resonance Raman spectroscopy and step-scan Fourier transform infrared (FTIR) spectroscopy have been used to identify the ligation state of ferrous heme iron for the H93G proximal cavity mutant of myoglobin in the absence of exogenous ligand on the proximal side. Preparation of the H93G mutant of myoglobin has been previously reported for a variety of axial ligands to the heme iron (e.g., substituted pyridines and imidazoles) [DePillis, G., Decatur, S. M,, Barrick, D., and Boxer, S. G. (1994) J. Am. Chem. Soc. 116, 6981-6982]. The present study examines the ligation states of heme in preparations of the H93G myoglobin with no exogenous ligand. In the deoxy form of H93G, resonance Raman spectroscopic evidence shows water to be the axial (fifth) ligand to the deoxy heme iron. Analysis of the infrared C-O and Raman Fe-C stretching frequencies for the CO adduct indicates that it is six-coordinate with a histidine trans ligand. Following photolysis of CO, a time-dependent change in ligation is evident in both step-scan FTIR and saturation resonance Raman spectra, leading to the conclusion that a conformationally driven ligand switch exists in the H93G protein. In the absence of exogenous nitrogenous ligands, the CO trans effect stabilizes endogenous histidine ligation, while conformational strain favors the dissociation of histidine following photolysis of CO. The replacement of histidine by water in the five-coordinate complex is estimated to occur in