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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >NMR study of the conformational transition of cytochrome c upon the displacement of Met80 by exogenous ligand: structural and magnetic characterization of azidoferricytochrome c.
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NMR study of the conformational transition of cytochrome c upon the displacement of Met80 by exogenous ligand: structural and magnetic characterization of azidoferricytochrome c.

机译：Met80被外源性配体取代后细胞色素c构象转变的NMR研究：叠氮铁蛋白细胞色素c的结构和磁性表征。

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摘要

As the exogenous ligand-cytochrome c complexes were purported to represent models for the unfolding intermediate of cytochrome c, NMR spectroscopy has been utilized to study the azide adduct of horse heart cytochrome c. The structure of azidoferricytochrome c was modeled by restrained energy minimization using paramagenetic pseudocontact shifts as constraints. The bound azide moiety was found to be tilted approximately 15 degrees from the heme normal. The displacement of Met80 by the exogenous azide molecule causes large structural rearrangement in the distal cavity. Furthermore, the conformation transition associated with the swing out of the loop containing Met80 and the shift of the 50s-helix increases the solvent accessibility of the heme group. To elucidate the heme electronic structure of the complex, the paramagnetic 13C shifts were analyzed in terms of a model based on the pi molecular orbitals of the heme under perturbed D(4) symmetry. It turned out that the Hisz.sbnd;Fe bonding provides the protein constraint that orients the in-plane anisotropy in the complex. The electronic properties are in accordance with the calculated magnetic susceptibility anisotropy and the structural information.
机译：由于外源性配体-细胞色素c络合物据称代表了细胞色素c展开中间体的模型，因此NMR光谱已被用于研究马心脏细胞色素c的叠氮化物加合物。叠氮铁蛋白细胞色素c的结构是通过使用准成因的伪接触位移作为约束，通过限制能量的最小化来建模的。发现结合的叠氮化物部分与血红素法线倾斜约15度。 Met80被外源叠氮化物分子置换会导致远端腔内发生较大的结构重排。此外，与包含Met80的环的摆动和50s-螺旋的移位相关的构象转变增加了血红素基团的溶剂可及性。为了阐明该复合物的血红素电子结构，在扰动的D（4）对称性下，基于血红素的pi分子轨道的模型对顺磁性13C位移进行了分析。事实证明，Hiszsbnd; Fe键提供了限制复合物中平面内各向异性的蛋白质约束。电子性质与计算的磁化率各向异性和结构信息一致。

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