Department of Molecular Medicine and ‡Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University , Ithaca, New York 14853, United States.
ACS Chem Biol. 2014 Jan 17;9(1):128-33. doi: 10.1021/cb4007166. Epub 2013 Nov 1.
Protein dimerization provides a mechanism for the modulation of cellular signaling events. In α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors, the rapidly desensitizing, activated state has been correlated with a weakly dimeric, glutamate-binding domain conformation. Allosteric modulators can form bridging interactions that stabilize the dimer interface. While most modulators can only bind to one position with a one modulator per dimer ratio, some thiazide-based modulators can bind to the interface in two symmetrical positions with a two modulator per dimer ratio. Based on small-angle X-ray scattering (SAXS) experiments, dimerization curves for the isolated glutamate-binding domain show that a second modulator binding site produces both an increase in positive cooperativity and a decrease in the EC50 for dimerization. Four body binding equilibrium models that incorporate a second dimer-stabilizing ligand were developed to fit the experimental data. The work illustrates why stoichiometry should be an important consideration during the rational design of dimerizing modulators.
蛋白质二聚化提供了一种调节细胞信号事件的机制。在α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）受体中，快速脱敏的激活状态与弱二聚体、谷氨酸结合域构象相关。变构调节剂可以形成桥接相互作用，稳定二聚体界面。虽然大多数调节剂只能与每个二聚体一个调节剂的一个位置结合，但一些基于噻嗪的调节剂可以以二聚体两个调节剂的两个对称位置与界面结合。基于小角度 X 射线散射（SAXS）实验，分离的谷氨酸结合域的二聚化曲线表明，第二个调节剂结合位点既增加了正协同性，又降低了二聚化的 EC50。开发了包含第二个二聚体稳定配体的四体结合平衡模型来拟合实验数据。这项工作说明了为什么在合理设计二聚化调节剂时，化学计量应该是一个重要的考虑因素。
