The study reports the high-resolution crystal structure of a human β2-adrenergic receptor (β2AR) fused with T4 lysozyme (β2AR-T4L) bound to the partial inverse agonist carazolol at 2.4 Å resolution. The structure provides a detailed view of a G protein-coupled receptor (GPCR) bound to a diffusible ligand. The second extracellular loop is positioned outside the binding cavity, facilitated by disulfide bridges and a short helical segment. Cholesterol in the crystal lattice mediates receptor-receptor interactions. Although the ligand-binding site of β2AR is similar to that of rhodopsin, structural differences highlight the challenges of using rhodopsin as a template for GPCRs. The structure reveals the receptor's topology, ligand-binding pocket, and differences from rhodopsin. The β2AR-T4L structure shows minimal interactions between the fusion protein and the receptor, with specific salt bridges and guanidinium interactions. The crystal packing involves lipid molecules, with ordered lipids mediating receptor-receptor contacts. The β2AR-T4L structure shows a distinct conformation compared to rhodopsin, with differences in helix orientations and ligand-binding site architecture. The structure also highlights the role of cholesterol in receptor signaling and the importance of lipid-mediated interactions. The study provides insights into the structural diversity of GPCRs and the challenges in modeling their ligand-binding sites. The findings contribute to understanding GPCR function and may aid in drug design.The study reports the high-resolution crystal structure of a human β2-adrenergic receptor (β2AR) fused with T4 lysozyme (β2AR-T4L) bound to the partial inverse agonist carazolol at 2.4 Å resolution. The structure provides a detailed view of a G protein-coupled receptor (GPCR) bound to a diffusible ligand. The second extracellular loop is positioned outside the binding cavity, facilitated by disulfide bridges and a short helical segment. Cholesterol in the crystal lattice mediates receptor-receptor interactions. Although the ligand-binding site of β2AR is similar to that of rhodopsin, structural differences highlight the challenges of using rhodopsin as a template for GPCRs. The structure reveals the receptor's topology, ligand-binding pocket, and differences from rhodopsin. The β2AR-T4L structure shows minimal interactions between the fusion protein and the receptor, with specific salt bridges and guanidinium interactions. The crystal packing involves lipid molecules, with ordered lipids mediating receptor-receptor contacts. The β2AR-T4L structure shows a distinct conformation compared to rhodopsin, with differences in helix orientations and ligand-binding site architecture. The structure also highlights the role of cholesterol in receptor signaling and the importance of lipid-mediated interactions. The study provides insights into the structural diversity of GPCRs and the challenges in modeling their ligand-binding sites. The findings contribute to understanding GPCR function and may aid in drug design.