Abstact

Opioid receptors signal through Gi/o protein and beta-arrestin pathways that mediate distinct effects of opiate drugs. While opioid binding and G protein activation are well studied, beta-arrestin recruitment remains poorly understood. Here, we determine the complex structure of the kappa opioid receptor (KOR) with beta-arrestin1 (betaarr1) at 2.60 A resolution using cryogenic electron microscopy. Structural and mass spectrometry analyses reveal multiple phosphorylation sites and a phospholipid-binding site that specifically enhances arrestin recruitment. The KOR-betaarr1 complex adopts a core interaction and exhibits notable differences from other GPCR-betaarr1 complexes. Comparisons with the structures of KOR-Nb39 and KOR-Gi1 complexes also reveal distinct structural features in the orthosteric binding site and the KOR-transducer interface that affect signaling bias. Using extensive 3D variation analysis and molecular dynamics simulations, we identify a range of conformational dynamics in both the receptor and betaarr1, suggesting an allosteric pathway for arrestin's entry and exit.