Proximal ligand motions in H93G myoglobin
Proximal ligand motions in H93G myoglobin
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DOI：
10.1046/j.1432-1033.2002.03193.x
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发表时间：
2002-10-01
期刊：
影响因子：
--
通讯作者：
Boxer, SG
中科院分区：
文献类型：
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作者：
Franzen, S;Peterson, ES;Boxer, SG
用共振拉曼光谱研究了肌红蛋白H 93 G近腔突变体的光产物光谱中铁-配体伸缩频率的变化。测量比较了H93 G（L）中血红素铁的脱氧亚铁态，其中L是结合在近端腔中的外源性咪唑配体，与H93 G（L）*CO在8 ns处的光解中间体。对于一系列甲基取代的咪唑类化合物，其光产物光谱中铁配体轴向面外模nu（Fe-L）的频率随L的性质不同而有显著差异.进一步与无外源配体存在下的肌红蛋白近腔突变体（H93 G）和H93 G的一氧化碳加合物的光产物（H93 G-*CO）进行比较。对于这种情况，已经表明H2O是H93 G脱氧形式的血红素铁的轴向（第五）配体。H93 G-*CO的光产物与推测为组氨酸的瞬时结合配体一致。这里提出的数据进一步证实了这样的结论，即构象驱动的配体开关存在于光解H93 G-* CO。结果表明，配体的构象变化响应于动态运动的球蛋白在纳秒和更长的时间尺度上的H93 G近端腔突变体的一般特征。
Resonance Raman spectroscopy has been used to observe changes in the iron-ligand stretching frequency in photoproduct spectra of the proximal cavity mutant of myoglobin H93G. The measurements compare the deoxy ferrous state of the heme iron in H93G(L), where L is an exogenous imidazole ligand bound in the proximal cavity, to the photolyzed intermediate of H93G(L)*CO at 8 ns. There are significant differences in the frequencies of the iron-ligand axial out-of-plane mode nu(Fe-L) in the photoproduct spectra depending on the nature of L for a series of methyl-substituted imidazoles. Further comparison was made with the proximal cavity mutant of myoglobin in the absence of exogenous ligand (H93G) and the photoproduct of the carbonmonoxy adduct of H93G (H93G-*CO). For this case, it has been shown that H2O is the axial (fifth) ligand to the heme iron in the deoxy form of H93G. The photoproduct of H93G-*CO is consistent with a transiently bound ligand proposed to be a histidine. The data presented here further substantiate the conclusion that a conformationally driven ligand switch exists in photolyzed H93G-*CO. The results suggest that ligand conformational changes in response to dynamic motions of the globin on the nanosecond and longer time scales are a general feature of the H93G proximal cavity mutant.