biostudies-literatureUnknown13(1)Deluigi Mα-adrenergic receptors (αARs) are G protein-coupled receptors that regulate vital functions of the cardiovascular and nervous systems. The therapeutic potential of αARs, however, is largely unexploited and hampered by the scarcity of subtype-selective ligands. Moreover, several aminergic drugs either show off-target binding to αARs or fail to interact with the desired subtype. Here, we report the crystal structure of human α_1BAR bound to the inverse agonist (+)-cyclazosin, enabled by the fusion to a DARPin crystallization chaperone. The α_1BAR structure allows the identification of two unique secondary binding pockets. By structural comparison of α_1BAR with α₂ARs, and by constructing α_1BAR-α_2CAR chimeras, we identify residues 3.29 and 6.55 as key determinants of ligand selectivity. Our findings provide a basis for discovery of α_1BAR-selective ligands and may guide the optimization of aminergic drugs to prevent off-target binding to αARs, or to elicit a selective interaction with the desired subtype.Nature communications382https://www.ebi.ac.uk/biostudies/studies/S-EPMC8770593biostudies-literatureCrystal structure of the α_1B-adrenergic receptor reveals molecular determinants of selective ligand recognition.PMC8770593Vaid TMCridge RRMittl PREPluckthun AKlenk CZerbe OChalmers DKEberle SADeluigi MScott DJMorstein LSchuster MKlipp AMerklinger LVacca Sde Zhang LAEgloff PfalseCrystal structure of the α_1B-adrenergic receptor reveals molecular determinants of selective ligand recognition.α-adrenergic receptors (αARs) are G protein-coupled receptors that regulate vital functions of the cardiovascular and nervous systems. The therapeutic potential of αARs, however, is largely unexploited and hampered by the scarcity of subtype-selective ligands. Moreover, several aminergic drugs either show off-target binding to αARs or fail to interact with the desired subtype. Here, we report the crystal structure of human α_1BAR bound to the inverse agonist (+)-cyclazosin, enabled by the fusion to a DARPin crystallization chaperone. The α_1BAR structure allows the identification of two unique secondary binding pockets. By structural comparison of α_1BAR with α₂ARs, and by constructing α_1BAR-α_2CAR chimeras, we identify residues 3.29 and 6.55 as key determinants of ligand selectivity. Our findings provide a basis for discovery of α_1BAR-selective ligands and may guide the optimization of aminergic drugs to prevent off-target binding to αARs, or to elicit a selective interaction with the desired subtype.2022-01-01T00:00:00Z2022 Jan2026-05-31T19:58:04.917Z2025-04-19T22:40:13.057ZS-EPMC87705933504641010.1038/s41467-021-27911-3