INAC, SYMMES , Université Grenoble Alpes, CEA, CNRS , F-38000 Grenoble , France.
Department of Inorganic and Analytical Chemistry , University of Szeged , Dóm tér 7 , Szeged H-6720 , Hungary.
Inorg Chem. 2018 May 21;57(10):5723-5731. doi: 10.1021/acs.inorgchem.7b02735. Epub 2018 Jan 12.
Peptide design is an efficient strategy to create relevant models of natural metal binding sites found in proteins. The two short tetrapeptides Ac-Cys-dPro-Pro-Cys-NH (CdPPC) and Ac-Cys-Pro-Gly-Cys-NH (CPGC) were synthesized and studied as mimics of Cu(I) binding sites involved in Cu homeostasis. Both sequences contain β turn inducing motifs to rigidify the peptide backbone structure and thereby preorganize the metal-binding side chains. The more constrained structure of the peptide CdPPC with respect to CPGC was evidenced by the measurements of the temperature coefficients of the amide protons by H NMR, which suggest a solvent-shielded intramolecular hydrogen bond in CdPPC, and no H-bond in CPGC. The Cu(I) complexes were studied by UV, circular dichroism (CD), and NMR spectroscopies as well as electrospray ionization mass spectrometry (ESI-MS) experiments in aqueous solution at physiological pH. The complexes formed with CPGC showed a complicated speciation with the possible formation of many polymetallic species. By contrast, the better preorganization in CdPPC leads to the formation of a unique CuL complex involving a CuS core. The formation of this specific cluster was confirmed by ESI-MS and by diffusion-ordered NMR spectroscopy in solution. The affinity of CdPPC for Cu(I) (β = 10 calculated for a CuL complex) is more than 1 order of magnitude larger than the affinity measured for the less constrained peptide CPGC. Besides, this stability constant value is very similar to those reported with proteins. Therefore, the Cu(I) complex formed with the simple tetrapeptide CdPPC in water at physiological pH represents a very good model of Cu(I)-thiolate clusters found in proteins. The extremely large selectivity (10) in favor of Cu(I) with respect to Zn(II), an abundant competitor in cells, makes it a promising candidate to be targeted to the liver cells for the localized treatment of Cu overload in Wilson's disease.
肽设计是一种有效的策略，可以创建天然金属结合位点的相关模型，这些天然金属结合位点存在于蛋白质中。合成了两个短的四肽 Ac-Cys-dPro-Pro-Cys-NH（CdPPC）和 Ac-Cys-Pro-Gly-Cys-NH（CPGC），并将其作为涉及铜稳态的 Cu（I）结合位点的模拟物进行了研究。这两个序列都包含β转角诱导基序，以刚性化肽主链结构，并预先组织金属结合侧链。通过 H NMR 测量酰胺质子的温度系数证明了肽 CdPPC 相对于 CPGC 的结构更为受限，这表明 CdPPC 中存在溶剂屏蔽的分子内氢键，而 CPGC 中不存在氢键。Cu（I）配合物在生理 pH 下的水溶液中通过 UV、圆二色性（CD）和 NMR 光谱以及电喷雾电离质谱（ESI-MS）实验进行了研究。与 CPGC 形成的配合物表现出复杂的形态，可能形成了许多多金属物种。相比之下，CdPPC 更好的预组织导致形成独特的 CuL 配合物，涉及 CuS 核。ESI-MS 和溶液中的扩散有序 NMR 光谱证实了这种特定簇的形成。CdPPC 与 Cu（I）的亲和力（β=10，计算得到一个 CuL 配合物）比与约束性较小的肽 CPGC 测量到的亲和力大 1 个数量级以上。此外，这个稳定常数的值与那些与蛋白质相关的报道非常相似。因此，在生理 pH 下的水中与简单的四肽 CdPPC 形成的 Cu（I）配合物代表了在蛋白质中发现的 Cu（I）-硫醇簇的非常好的模型。与 Zn（II）相比，对 Cu（I）的选择性（10）非常大，Zn（II）是细胞中丰富的竞争者，这使其成为针对威尔逊病中铜过载的肝细胞进行局部治疗的有前途的候选物。
