A high-resolution description of β1-adrenergic receptor functional dynamics and allosteric coupling from backbone NMR
Anne Grahl, Layara Akemi Abiko, Shin Isogai, Timothy Sharpe, Stephan Grzesiek
Abstract
Abstract Signal transmission and regulation of G-protein-coupled receptors (GPCRs) by extra- and intracellular ligands occurs via modulation of complex conformational equilibria, but their exact kinetic details and underlying atomic mechanisms are unknown. Here we quantified these dynamic equilibria in the β 1 -adrenergic receptor in its apo form and seven ligand complexes using 1 H/ 15 N NMR spectroscopy. We observe three major exchanging conformations: an inactive conformation ( C i ), a preactive conformation ( C p ) and an active conformation ( C a ), which becomes fully populated in a ternary complex with a G protein mimicking nanobody. The C i ↔ C p exchange occurs on the microsecond scale, the C p ↔ C a exchange is slower than ~5 ms and only occurs in the presence of two highly conserved tyrosines (Y 5.58 , Y 7.53 ), which stabilize the active conformation of TM6. The C p → C a chemical shift changes indicate a pivoting motion of the entire TM6 that couples the effector site to the orthosteric ligand pocket.