Mendola Diego La, Magrì Antonio, Hansson Orjan, Bonomo Raffaele P, Rizzarelli Enrico
Istituto di Biostrutture e Bioimmagini-CNR-Catania, Italy.
J Inorg Biochem. 2009 May;103(5):758-65. doi: 10.1016/j.jinorgbio.2009.01.017. Epub 2009 Jan 29.
Copper(II) complexes of the peptide fragment (Dpl122-130) encompassing the sequence 122-130 of human doppel protein were characterized by potentiometric, UV-Visible, CD and EPR spectroscopic methods. An analogous peptide, in which the aspartate residue was substituted by an asparagine amino acid, was synthesized in order to provide evidence on the possible role of carboxylate group in copper(II) coordination. It was found that the carboxylic group is directly involved in copper(II) coordination at acidic pH, forming the CuLH(2) species with Dpl122-130. This copper(II) complex displayed EPR parameters very similar to those of the analogous complex with the whole doppel protein. At pH higher than 7, the complexes showed magnetic parameters similar to those of the major species of protein formed in the pH range 7-8, with the metal coordination environment consisting of one imidazole and three amide nitrogen atoms. The comparison of Cu-Dpl122-130 binding constant values with those of the prion peptide fragments (PrP106-114), showed that doppel peptide had a higher metal binding affinity at acidic pH whereas the prion peptide fragment binds the metal tightly at physiological pH.
采用电位滴定法、紫外可见光谱法、圆二色光谱法和电子顺磁共振光谱法对包含人类多普蛋白122 - 130序列的肽片段（Dpl122 - 130）的铜（II）配合物进行了表征。合成了一种类似的肽，其中天冬氨酸残基被天冬酰胺氨基酸取代，以便为羧酸根基团在铜（II）配位中可能发挥的作用提供证据。研究发现，在酸性pH值下，羧基直接参与铜（II）配位，与Dpl122 - 130形成CuLH(2)物种。该铜（II）配合物的电子顺磁共振参数与含有完整多普蛋白的类似配合物非常相似。在pH值高于7时，这些配合物的磁参数与在pH值7 - 8范围内形成的主要蛋白质物种的磁参数相似，其金属配位环境由一个咪唑和三个酰胺氮原子组成。将Cu - Dpl122 - 130的结合常数与朊病毒肽片段（PrP106 - 114）的结合常数进行比较，结果表明，多普肽在酸性pH值下具有更高的金属结合亲和力，而朊病毒肽片段在生理pH值下能紧密结合金属。
