Gene

Cell biology

Biology

Receptor

Mutation

Signal transduction

Biochemistry

Drug discovery

G protein

G protein-coupled receptor

Angiotensin II

Mutagenesis

Allosteric regulation

Angiotensin II receptor type 1

Chemistry

Biophysics

Nature Communications

G protein-coupled receptors (GPCRs) are the most common proteins targeted by approved drugs. A complete mechanistic elucidation of large-scale conformational transitions underlying the activation mechanisms of GPCRs is of critical importance for therapeutic drug development. Here, we apply a combined computational and experimental framework integrating extensive molecular dynamics simulations, Markov state models, site-directed mutagenesis, and conformational biosensors to investigate the conformational landscape of the angiotensin II (AngII) type 1 receptor (AT 1 receptor) — a prototypical class A GPCR—activation. Our findings suggest a synergistic transition mechanism for AT 1 receptor activation. A key intermediate state is identified in the activation pathway, which possesses a cryptic binding site within the intracellular region of the receptor. Mutation of this cryptic site prevents activation of the downstream G protein signaling and β-arrestin-mediated pathways by the endogenous AngII octapeptide agonist, suggesting an allosteric regulatory mechanism. Together, these findings provide a deeper understanding of AT 1 receptor activation at an atomic level and suggest avenues for the design of allosteric AT 1 receptor modulators with a broad range of applications in GPCR biology, biophysics, and medicinal chemistry.

Activation pathway of a G protein-coupled receptor uncovers conformational intermediates as targets for allosteric drug design