Rapid and accurate mapping of ligand binding and structural changes in the β-1 adrenergic receptor using carbene footprinting and mass spectrometry

Abstract

G protein coupled receptors (GPCRs) control many physiological processes and are major targets for therapeutic intervention. As transmembrane proteins with inherent instability they are often difficult study with more conventional structural methods. Here we report the use of carbene footprinting to map ligand binding and structural changes in the β1-adrenergic receptor, β1AR, a GPCR target of beta-blocker drugs. The method revealed differences between binding of the agonist, isoprenaline, and the reverse agonist, carazalol, both in terms of their occupancy of the orthosteric ligand binding site and their effects on key regulatory structural features of β1AR including the ‘ionic lock’ between transmembrane (TM) helicies 3 and 6. Addition of nanobodies (Nbs) known to stabilise the activated complex (Nb80) and inactivated complex (Nb60) of β1AR induced further structural changes above those seen with the ligands alone. This repository entry contains the raw MS data in support of this work.