G protein-coupled receptors (GPCRs) are privileged structural scaffolds in biology that have the versatility to regulate diverse physiological processes. Interestingly, many GPCR ligands exhibit significant ‘bias’ – the ability to preferentially activate subsets of the many cellular pathways downstream of these receptors. Recently, complementary information from structural and spectroscopic approaches has made significant inroads into understanding the mechanisms of these biased ligands. The consistently emerging theme is that GPCRs are highly dynamic proteins, and ligands with varying pharmacological properties differentially modulate the equilibrium among multiple conformations. Biased signaling and other recently appreciated complexities of GPCR signaling thus appear to be a natural consequence of the conformational heterogeneity of GPCRs and GPCR–transducer complexes.

G蛋白偶联受体（GPCR）是生物学中的特殊结构支架，具有调节多种生理过程的多功能性。有趣的是，许多 GPCR 配体表现出显着的“偏向”——优先激活这些受体下游许多细胞通路子集的能力。最近，来自结构和光谱方法的补充信息在理解这些偏向配体的机制方面取得了重大进展。不断出现的主题是 GPCR 是高度动态的蛋白质，具有不同药理学特性的配体差异性地调节多种构象之间的平衡。因此，偏向信号传导和最近认识到的 GPCR 信号传导的其他复杂性似乎是 GPCR 和 GPCR-转导复合物构象异质性的自然结果。