Cao Chunyang, Zhang Qi, Wang Zhi-Qiang, Wang Yue-Feng, Wang Yun-Hua, Wu Houming, Huang Zhong-Xian
State Key Laboratory of Bio-organic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Feng Lin Lu (Road), Shanghai 200032, China.
Biochimie. 2003 Oct;85(10):1007-16. doi: 10.1016/j.biochi.2003.08.005.
1D and 2D (1)H NMR were employed to probe the effects on the heme microenvironment of cytochrome b(5) caused by the mutation from Val45 to Tyr45, His45 and Glu45. Compared with wild type (WT) cytochrome b(5), in all mutants the heme ring are CCW rotated relative to the imidazole planes of axial ligands and the angles beta between two axial ligand imidazole planes are not changed, being in agreement with the temperature dependence of the shifts of the heme protons. The ratios of heme isomers (major to minor) are smaller than that in WT. The 4-vinyl group of the heme in V45Y assumes cis-orientation, being similar to that of WT, while in V45E and V45H, both cis and trans orientation are found. The relationships between the structure and biological function of the mutants are discussed in terms of the geometry of heme and axial ligands, the hydrophobicity of heme pocket and the electrostatic potential of the heme-exposed area.
采用一维和二维（1）H NMR来探究缬氨酸45突变为酪氨酸45、组氨酸45和谷氨酸45对细胞色素b（5）血红素微环境的影响。与野生型（WT）细胞色素b（5）相比，在所有突变体中，血红素环相对于轴向配体的咪唑平面逆时针旋转，且两个轴向配体咪唑平面之间的β角不变，这与血红素质子位移的温度依赖性一致。血红素异构体（主要与次要）的比例小于野生型中的比例。V45Y中血红素的4-乙烯基呈顺式取向，与野生型相似，而在V45E和V45H中，同时发现了顺式和反式取向。根据血红素和轴向配体的几何结构、血红素口袋的疏水性以及血红素暴露区域的静电势，讨论了突变体的结构与生物学功能之间的关系。
