Structural equilibrium underlying ligand-dependent activation of β 2-adrenoreceptor

Nat Chem Biol. 2020 Apr;16(4):430-439. doi: 10.1038/s41589-019-0457-5. Epub 2020 Jan 20.

Abstract

G-protein-coupled receptors (GPCRs) are seven-transmembrane proteins mediating cellular signals in response to extracellular stimuli. Although three-dimensional structures showcase snapshots that can be sampled in the process and nuclear magnetic resonance detects conformational equilibria, the mechanism by which agonist-activated GPCRs interact with various effectors remains elusive. Here, we used paramagnetic nuclear magnetic resonance for leucine amide resonances to visualize the structure of β2-adrenoreceptor in the full agonist-bound state, without thermostabilizing mutations abolishing its activity. The structure exhibited a unique orientation of the intracellular half of the transmembrane helix 6, forming a cluster of G-protein-interacting residues. Furthermore, analyses of efficacy-dependent chemical shifts of the residues near the pivotal PIF microswitch identified an equilibrium among three conformations, including one responsible for the varied signal level in each ligand-bound state. Together, these results provide a structural basis for the dynamic activation of GPCRs and shed light on GPCR-mediated signal transduction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crystallography, X-Ray / methods
  • Humans
  • Ligands
  • Magnetic Resonance Spectroscopy / methods
  • Membrane Proteins / metabolism
  • Models, Molecular
  • Protein Binding / physiology
  • Protein Conformation
  • Receptors, Adrenergic, beta-2 / metabolism*
  • Receptors, Adrenergic, beta-2 / ultrastructure*
  • Receptors, G-Protein-Coupled / metabolism
  • Signal Transduction / physiology

Substances

  • Ligands
  • Membrane Proteins
  • Receptors, Adrenergic, beta-2
  • Receptors, G-Protein-Coupled