Rauschenberg Melanie, Bandaru Sateesh, Waller Mark P, Ravoo Bart Jan
Chemistry. 2014 Mar 3;20(10):2770-82. doi: 10.1002/chem.201303777.
A broad spectrum of physiological processes is mediated by highly specific noncovalent interactions of carbohydrates and proteins. In a recent communication we identified several cyclic hexapeptides in a dynamic combinatorial library that interact selectively with carbohydrates with high binding constants in water. Herein, we report a detailed investigation of the noncovalent interaction of two cyclic hexapeptides (Cys-His-Cys (which we call HisHis) and Cys-Tyr-Cys (which we call TyrTyr)) with a selection of monosaccharides and disaccharides in aqueous solution. The parallel and antiparallel isomers of HisHis or TyrTyr were synthesized separately, and their interaction with monosaccharides and disaccharides in aqueous solution was studied by isothermal titration calorimetry, NMR spectroscopic titrations, and circular dichroism spectroscopy. From these measurements, we identified particularly stable complexes (Ka> 1000 M(-1)) of the parallel isomer of HisHis with N-acetylneuraminic acid and with methyl-a-d-galactopyranoside as well as of both isomers of TyrTyr with trehalose. To gain further insight into the structure of the peptide–carbohydrate complexes, structure prediction was performed using quantum chemical methods. The calculations confirm the selectivity observed in the experiments and indicate the formation of multiple intermolecular hydrogen bonds in the most stable complexes.
碳水化合物和蛋白质之间高度特异性的非共价相互作用介导了广泛的生理过程。在最近的一篇通讯文章中，我们在一个动态组合文库中鉴定出了几种环状六肽，它们在水中能以高结合常数与碳水化合物选择性相互作用。在此，我们报告了对两种环状六肽（半胱氨酸-组氨酸-半胱氨酸（我们称之为HisHis）和半胱氨酸-酪氨酸-半胱氨酸（我们称之为TyrTyr））与一系列单糖和双糖在水溶液中的非共价相互作用的详细研究。分别合成了HisHis或TyrTyr的平行异构体和反平行异构体，并通过等温滴定量热法、核磁共振光谱滴定法和圆二色光谱法研究了它们与水溶液中单糖和双糖的相互作用。通过这些测量，我们确定了HisHis的平行异构体与N-乙酰神经氨酸和甲基-α-D-吡喃半乳糖苷以及TyrTyr的两种异构体与海藻糖形成的特别稳定的复合物（Ka>1000 M⁻¹）。为了进一步深入了解肽-碳水化合物复合物的结构，使用量子化学方法进行了结构预测。计算结果证实了实验中观察到的选择性，并表明在最稳定的复合物中形成了多个分子间氢键。
