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首页> 外文期刊>Biochemistry >Effects of Protein Structure on Iron-Polypeptide Vibrational Dynamic Coupling in Cytochrome c
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Effects of Protein Structure on Iron-Polypeptide Vibrational Dynamic Coupling in Cytochrome c

机译：蛋白质结构对细胞色素c中铁多肽振动动态耦合的影响

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摘要

Cytochrome c (Cyt c) has a heme covalently bound to the polypeptide via a Cys-X-X-Cys-His (CXXCH) linker that is located in the interface region for protein-protein interactions. To determine whether the polypeptide matrix influences iron vibrational dynamics, nuclear resonance vibrational spectroscopy (NRVS) measurements were performed on Fe-57-labeled ferric Hydrogenobacter thermophilus cytochrome c-552, and variants M13V, M13V/K22M, and A7F, which have structural modifications that alter the composition or environment of the CXXCH pentapeptide loop. Simulations of the NRVS data indicate that the 150-325 cm(-1) region is dominated by N-His-Fe-S-Met axial ligand and polypeptide motions, while the 325-400 cm(-1) region shows dominant contributions from nu(Fe-N-Pyr) (Pyr = pyrrole) and other heme-based modes. Diagnostic spectral signatures that directly relate to structural features of the heme active site are identified using a quantum chemistry-centered normal coordinate analysis (QCC-NCA). In particular, spectral features that directly correlate with CXXCH loop stiffness, the strength of the Fe-His interaction, and the degree of heme distortion are identified. Cumulative results from our investigation suggest that compared to the wild type (wt), variants M13V and M13V/K22M have a more rigid CXXCH pentapeptide segment, a stronger Fe-N-His interaction, and a more ruffled heme. Conversely, the A7F variant has a more planar heme and a weaker Fe-N-His bond. These results are correlated to the observed changes in reduction potential between wt protein and the variants studied here. Implications of these results for Cyt c biogenesis and electron transfer are also discussed.
机译：细胞色素c（Cyt c）具有通过位于蛋白质-蛋白质相互作用界面区域的Cys-X-X-Cys-His（CXXCH）接头与多肽共价结合的血红素。为了确定多肽基质是否影响铁的振动动力学，对铁-57标记的铁嗜热氢杆菌细胞色素c-552以及具有结构修饰的变体M13V，M13V / K22M和A7F进行了核磁共振波谱（NRVS）测量会改变CXXCH五肽环的组成或环境。 NRVS数据的模拟表明150-325 cm（-1）区域由N-His-Fe-S-Met轴向配体和多肽运动控制，而325-400 cm（-1）区域则显示nu（Fe-N-Pyr）（Pyr =吡咯）和其他基于血红素的模式。使用以量子化学为中心的正态坐标分析（QCC-NCA），可以识别与血红素活性位点的结构特征直接相关的诊断光谱特征。特别是，确定了与CXXCH回路刚度，Fe-His相互作用的强度以及血红素畸变程度直接相关的光谱特征。我们调查的累积结果表明，与野生型（wt）相比，变体M13V和M13V / K22M具有更刚性的CXXCH五肽片段，更强的Fe-N-His相互作用和更皱纹的血红素。相反，A7F变体具有更高的平面血红素和较弱的Fe-N-His键。这些结果与观察到的wt蛋白与此处研究的变体之间的还原电位变化相关。还讨论了这些结果对Cyt c生物发生和电子转移的影响。

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