FT-infrared spectroscopic studies of the iron ligand CO stretch mode of iNOS oxygenase domain: Effect of arginine and tetrahydrobiopterin
FT-infrared spectroscopic studies of the iron ligand CO stretch mode of iNOS oxygenase domain: Effect of arginine and tetrahydrobiopterin
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DOI：
10.1021/bi0003792
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发表时间：
2000-08-22
期刊：
影响因子：
2.9
通讯作者：
Ghosh, DK
中科院分区：
文献类型：
--
作者：
Jung, C;Stuehr, DJ;Ghosh, DK
本文研究了诱导型一氧化氮合酶加氧酶结构域(INOSox)在20-298K温度范围内的铁配体CO伸缩振动模式。iNOSox在没有精氨酸的情况下发现了两个主要构象亚态随温度变化的平衡，CO伸展带集中在1945和1954 cm(-1)附近。当四氢生物蝶呤(H4B)结合时，这种行为不会发生质的改变。精氨酸结合显著地改变了光谱，在约1905 cm(-1)处形成了尖锐的CO伸缩模带，表明与CO配体形成了氢键。当温度低于250K时，伸缩振动频率随温度的降低几乎呈线性下降，表明CO配体与活性中心的精氨酸/蛋白质之间通过氢键发生了很强的偶联。在25K下进行的CO配体的闪光光解揭示了捕获在血红素口袋中的光解离的CO配体的CO伸展模式。光解离的CO的伸缩振动频率与铁结合的CO的伸缩振动频率之间存在着负的线性关系，说明光解离的配体位于血红素附近。
The iron ligand CO stretch vibration mode of the inducible nitric oxide synthase oxygenase domain (iNOSox) has been studied from 20 to 298 K. iNOSox in the absence of arginine reveals a temperature-dependent equilibrium of two major conformational substates with CO stretch bands centered at about 1945 and 1954 cm(-1). This behavior is not qualitatively changed when tetrahydrobiopterin (H4B) is bound. Arginine binding changes significantly the spectrum by formation of a sharp CO stretch mode band at about 1905 cm(-1) and indicates the formation of a hydrogen bond to the CO ligand. For temperatures lower than 250 K, the stretch vibration frequency decreases almost linearly with decreasing temperature and indicates that the coupling between the CO ligand and the arginine/protein in the active site via the hydrogen bond is very strong. Flashphotolysis of the CO ligand carried out at 25 K revealed the CO stretch mode of the photodissociated CO ligand trapped in the heme pocket. There is a negative linear relation between the stretch vibration frequencies of the photodissociated and the iron-bound CO indicating that the photodissociated ligand stays near the heme.