Activation dynamics traced through a G protein–coupled receptor by 81 ¹ H- ¹⁵ N NMR probes

The regulation of G protein-coupled receptor signaling by different orthosteric ligands is thought to occur through shifts in dynamically interconverting, conformational distributions. Such changes in dynamical distributions have been detected so far only by very sparse, often non-native experimental probes at low resolution. Using a recently developed paramagnetic nuclear magnetic resonance (NMR) method, we could assign and follow 81 ¹H-¹⁵N NMR correlations in the β₁-adrenergic receptor β₁AR at ambient conditions in response to various orthosteric ligands in the absence or presence of a G protein-mimicking nanobody. The comparison reveals the dynamics and mechanism of the central, highly conserved xWIPF₃ motif, contiguous regions of rigid and loose conformational coupling separated by conserved prolines during signal transmission, and the plasticity of the intracellular face in response to transducer binding.