Stanczak Pawel, Valensin Daniela, Juszczyk Paulina, Grzonka Zbigniew, Migliorini Caterina, Molteni Elena, Valensin Gianni, Gaggelli Elena, Kozlowski Henryk
Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie 14, 50-383 Wroclaw, Poland.
Biochemistry. 2005 Oct 4;44(39):12940-54. doi: 10.1021/bi051177e.
Prion protein (PrP) misfolding is one of the pivotal issues in understanding the rudiments of neurodegenerative disorders. The conformational change of mammalian cellular PrP to scrapie PrP is caused by an unknown agent, but there is reasonable evidence supporting the key role of copper ions in this process. The structure of the avian PrP was found to be very similar to the mammalian protein, although there is only 30% homology in the secondary structure. This work shows that copper ions are very effectively bound by hexarepeat fragments of chicken prion protein, although not as effectively as it was found in the case of mammalian protein. By means of potentiometric and spectroscopic techniques (nuclear magnetic resonance, circular dichroism, UV-vis, and electronic paramagnetic resonance), it was shown that Cu(II) ions coordinate to the chicken PrP hexapeptide domain in physiological pH via imidazole nitrogen donors of His residue(s). The binding pattern changes the structure of peptide involved, indicating a possible impact of Cu(II) ions in the biology and pathology of nonmammalian PrP, which could be similar to that found for mammalian PrP. The present study shows that, similar to the human prion octapeptide repeats, chicken prion hexapeptide repeats might bind copper ions in two different ways, depending on the number of repeats and metal/ligand molar ratio: (i) an intra-repeat coordination mode in which copper ion is chelated by His imidazole and deprotonated amide nitrogen in monomeric peptide and (ii) an inter-repeat coordination mode in which a polymeric peptide ligand (dimer and trimer) forms polyimidazole complexes that are very stable at physiological pH. Two proline residues inserted into the hexapeptide unit have a critical impact on the metal-binding ability.
朊病毒蛋白（PrP）的错误折叠是理解神经退行性疾病基本原理的关键问题之一。哺乳动物细胞PrP向瘙痒病PrP的构象变化是由一种未知因子引起的，但有合理证据支持铜离子在此过程中的关键作用。尽管二级结构仅有30%的同源性，但发现禽类PrP的结构与哺乳动物蛋白非常相似。这项研究表明，鸡朊病毒蛋白的六肽重复片段能非常有效地结合铜离子，尽管不如在哺乳动物蛋白中那样有效。通过电位滴定和光谱技术（核磁共振、圆二色性、紫外可见光谱和电子顺磁共振）表明，在生理pH值下，Cu（II）离子通过His残基的咪唑氮供体与鸡PrP六肽结构域配位。这种结合模式改变了相关肽段的结构，表明Cu（II）离子可能对非哺乳动物PrP的生物学和病理学产生影响，这可能与在哺乳动物PrP中发现的情况类似。本研究表明，与人类朊病毒八肽重复序列类似，鸡朊病毒六肽重复序列可能以两种不同方式结合铜离子，这取决于重复序列的数量和金属/配体摩尔比：（i）一种重复序列内配位模式，其中铜离子在单体肽中被His咪唑和去质子化的酰胺氮螯合；（ii）一种重复序列间配位模式，其中聚合肽配体（二聚体和三聚体）形成在生理pH值下非常稳定的多咪唑配合物。插入六肽单元的两个脯氨酸残基对金属结合能力有至关重要的影响。
