Université catholique de Louvain, Louvain Institute of Biomolecular Science and Technology, 1348, Louvain-la-Neuve, Belgium.
Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore.
Commun Biol. 2020 Dec 18;3(1):786. doi: 10.1038/s42003-020-01518-8.
A current challenge to produce effective therapeutics is to accurately determine the location of the ligand-biding site and to characterize its properties. So far, the mechanisms underlying the functional activation of cell surface receptors by ligands with a complex binding mechanism remain poorly understood due to a lack of suitable nanoscopic methods to study them in their native environment. Here, we elucidated the ligand-binding mechanism of the human G protein-coupled C5a receptor (C5aR). We discovered for the first time a cooperativity between the two orthosteric binding sites. We found that the N-terminus C5aR serves as a kinetic trap, while the transmembrane domain acts as the functional site and both contributes to the overall high-affinity interaction. In particular, Asp282 plays a key role in ligand binding thermodynamics, as revealed by atomic force microscopy and steered molecular dynamics simulation. Our findings provide a new structural basis for the functional and mechanistic understanding of the GPCR family that binds large macromolecular ligands.
目前，开发有效治疗方法的一个挑战是准确确定配体结合位点的位置，并对其特性进行描述。到目前为止，由于缺乏合适的纳米级方法来在其天然环境中研究这些配体，因此对于具有复杂结合机制的配体激活细胞表面受体的功能机制仍然知之甚少。在这里，我们阐明了人 G 蛋白偶联 C5a 受体（C5aR）的配体结合机制。我们首次发现了两个正位结合位点之间的协同作用。我们发现 C5aR 的 N 端充当动力学陷阱，而跨膜结构域充当功能位点，两者都有助于整体高亲和力相互作用。特别是，原子力显微镜和导向分子动力学模拟揭示了天冬氨酸 282 在配体结合热力学中起着关键作用。我们的研究结果为理解结合大分子配体的 GPCR 家族的功能和机制提供了新的结构基础。
