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The human β1-adrenoceptor (β1AR) is a G-protein-coupled receptor (GPCR) involved in sympathetic system regulation through agonist-induced activation. The conserved CWXP-motif in helix 6 (rotamer toggle switch) is one of the most important activation switches in Class A GPCRs. In order to investigate how the agonist binding disturbs this switch, we carried out molecular dynamics simulations of a hβ1AR model in the apo and R-noradrenaline-bound forms. The results show that the agonist binding changes the β1-angle distribution of Cys336, Trp337 and Phe341 residues and increases the helix 6 bending. Overall, we provide a functional hβ1AR model, showing how the rotamer toggle switch mechanism works at atomic level. [ABSTRACT FROM PUBLISHER]

The human β1-adrenoceptor (hβ1AR) is a transmembrane (TM) protein responsible for the signal transduction pathway via agonist interaction. Despite its importance, hβ1AR activation mechanism is still unclear. The most studied and widely accepted mechanism is the disruption of a salt bridge between TM3 arginine and TM6 glutamic acid, called ionic lock. In this work, we constructed a functional hβ1AR-model equilibrated in a membrane environment to study the influence of agonist binding on the dynamical behaviour of hβ1AR and on the opening of the ionic lock. The results indicate that the agonist (R-noradrenaline) disturbs the hβ1AR, causing a TM helices rotation, disrupting the ionic lock. This rotational motion occurs in opposite directions in the intercellular and extracellular domains of hβ1AR, opening the ionic lock. [ABSTRACT FROM AUTHOR]