The study by Rasmussen et al. (2011) reports the structure of a nanobody-stabilized active state of the β2 adrenoceptor (β2AR). The researchers used a camelid antibody fragment (nanobody) that exhibits G protein-like behavior to stabilize an active state of the β2AR. This nanobody, Nb80, was shown to bind efficiently to agonist-occupied β2AR and produce changes in fluorescence that are similar to those observed in the presence of Gs and isoproterenol. The high-resolution structure of the β2AR-Nb80 complex revealed subtle changes in the ligand-binding pocket and significant rearrangements in the cytoplasmic regions of transmembrane segments 5, 6, and 7, which are similar to those observed in opsin, an active form of rhodopsin. These structural changes provide insights into the process of agonist binding and activation of the β2AR. The study also highlights the importance of the nanobody in stabilizing an active conformation of the receptor, mimicking the effect of Gs.The study by Rasmussen et al. (2011) reports the structure of a nanobody-stabilized active state of the β2 adrenoceptor (β2AR). The researchers used a camelid antibody fragment (nanobody) that exhibits G protein-like behavior to stabilize an active state of the β2AR. This nanobody, Nb80, was shown to bind efficiently to agonist-occupied β2AR and produce changes in fluorescence that are similar to those observed in the presence of Gs and isoproterenol. The high-resolution structure of the β2AR-Nb80 complex revealed subtle changes in the ligand-binding pocket and significant rearrangements in the cytoplasmic regions of transmembrane segments 5, 6, and 7, which are similar to those observed in opsin, an active form of rhodopsin. These structural changes provide insights into the process of agonist binding and activation of the β2AR. The study also highlights the importance of the nanobody in stabilizing an active conformation of the receptor, mimicking the effect of Gs.