Yamamoto Y
Department of Chemistry, University of Tsukuba, Ibaraki.
J Biochem. 1996 Jan;119(1):16-22. doi: 10.1093/oxfordjournals.jbchem.a021202.
The molecular structure of the active site of horse heart met-cyano cytochrome c, as a function of temperature, has been investigated using 1H-NMR. A temperature dependence study of the NMR spectra revealed that one heme methyl proton resonance exhibits anti-Curie behavior, i.e., the hyperfine shift increases with increasing temperature. Analyses of the average heme methyl proton hyperfine shift and the proximal His imidazole proton resonances indicated that the iron-His bonding interaction in this protein is essentially independent of temperature. Since such an anomalous temperature dependence of the heme methyl proton resonance disappears in met-cyano complex of a heme peptide prepared by enzymatic degradation of the protein [Smith, M. and McLendon, G. (1981) J. Am. Chem. Soc. 103, 4912-4921], the anti-Curie behavior observed for the heme methyl proton resonance in met-cyano cytochrome c is attributed to a rotational displacement of the heme about the iron-His bond relative to the protein moiety due to a temperature-dependent conformational alteration of the heme-protein linkage. Such rotational mobility of heme at the active site of a protein may be responsible for the anomalous temperature dependence of heme methyl proton hyperfine shifts reported for many c-type ferri cytochromes.
利用1H-NMR研究了马心高铁氰化细胞色素c活性位点的分子结构与温度的关系。对NMR光谱的温度依赖性研究表明，一个血红素甲基质子共振呈现反居里行为，即超精细位移随温度升高而增加。对平均血红素甲基质子超精细位移和近端组氨酸咪唑质子共振的分析表明，该蛋白质中铁-组氨酸的键合相互作用基本上与温度无关。由于通过蛋白质的酶促降解制备的血红素肽的高铁氰化络合物中，血红素甲基质子共振的这种异常温度依赖性消失了[史密斯，M.和麦克伦登，G.（1981年）《美国化学会志》103，4912 - 4921]，在高铁氰化细胞色素c中观察到的血红素甲基质子共振的反居里行为归因于由于血红素-蛋白质连接的温度依赖性构象改变，血红素围绕铁-组氨酸键相对于蛋白质部分的旋转位移。蛋白质活性位点处血红素的这种旋转流动性可能是许多c型高铁细胞色素报道的血红素甲基质子超精细位移异常温度依赖性的原因。
