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Publication Abstract from PubMed

Salmeterol is a partial agonist for the beta2 adrenergic receptor (beta2AR) and the first long-acting beta2AR agonist to be widely used clinically for the treatment of asthma and chronic obstructive pulmonary disease. Salmeterol's safety and mechanism of action have both been controversial. To understand its unusual pharmacological action and partial agonism, we obtained the crystal structure of salmeterol-bound beta2AR in complex with an active-state-stabilizing nanobody. The structure reveals the location of the salmeterol exosite, where sequence differences between beta1AR and beta2AR explain the high receptor-subtype selectivity. A structural comparison with the beta2AR bound to the full agonist epinephrine reveals differences in the hydrogen-bond network involving residues Ser204(5.43) and Asn293(6.55). Mutagenesis and biophysical studies suggested that these interactions lead to a distinct active-state conformation that is responsible for the partial efficacy of G-protein activation and the limited beta-arrestin recruitment for salmeterol.

Structural insights into binding specificity, efficacy and bias of a beta2AR partial agonist.,Masureel M, Zou Y, Picard LP, van der Westhuizen E, Mahoney JP, Rodrigues JPGLM, Mildorf TJ, Dror RO, Shaw DE, Bouvier M, Pardon E, Steyaert J, Sunahara RK, Weis WI, Zhang C, Kobilka BK Nat Chem Biol. 2018 Nov;14(11):1059-1066. doi: 10.1038/s41589-018-0145-x. Epub, 2018 Oct 16. PMID:30327561^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.