title: Coupled Motions in β2AR:Gαs Conformational Ensembles.
abstract: G protein-coupled receptors (GPCRs) act as conduits in the plasma membrane, facilitating cellular responses to physiological events by activating intracellular signal transduction pathways. Extracellular signaling molecules can induce conformational changes in GPCR, which allow it to selectively activate intracellular protein partners such as heterotrimeric protein G. However, a major unsolved problem is how GPCRs and G proteins form complexes and how their interaction results in G protein activation. Here, we show that an inactive, agonist-free β2AR:Gαs complex can collectively sample intermediate states of the receptor on an activation pathway. An in silico conformational ensemble around the inactive state manifests significant conformational coupling between structural elements implicated in G protein activation throughout the complex. While Gαs helix α5 has received much attention as a driver for nucleotide exchange, we also observe interactions between helix αN with Intra Cellular Loop 2, which can be transmitted by β1 to facilitate nucleotide exchange by disrupting a salt bridge between the P-loop and Switch I. These interactions are moderated in an active state ensemble. Collectively, our results support an alternative view of G protein activation, in which precoupling can allosterically modulate an agonist-free receptor. Subsequent selective agonist recruitment would result in collective activation of the complex. This alternative view can help us understand how distinct extracellular binding partners result in different but interdependent signaling pathways, with broad implications for GPCR drug discovery.
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.|Division of Biosciences, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States.
authors.forename: Dimitar V
authors.initials: DV
authors.lastname: Pachov
authors.affiliation: Division of Biosciences, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States.|AMIB INRIA - Bioinformatics group, LIX, École Polytechnique , 91128 Palaiseau, France.
authors.forename: Rasmus
authors.initials: R
authors.lastname: Fonseca
authors.affiliation: INRIA Saclay-Île de France , 1 rue Honoré d'Estienne d'Orves, Bâtiment Alan Turing, Campus de l'École Polytechnique, 91120 Palaiseau, France.|Laboratoire d'Informatique de l'École Polytechnique (LIX), CNRS UMR 7161, École Polytechnique , 91128 Palaiseau, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Arnol
authors.affiliation: INRIA Saclay-Île de France , 1 rue Honoré d'Estienne d'Orves, Bâtiment Alan Turing, Campus de l'École Polytechnique, 91120 Palaiseau, France.|Laboratoire d'Informatique de l'École Polytechnique (LIX), CNRS UMR 7161, École Polytechnique , 91128 Palaiseau, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Bernauer
authors.affiliation: Division of Biosciences, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States.
authors.forename: Henry
authors.initials: H
authors.lastname: van den Bedem
mesh_terms: D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D009068:Movement; D011487:Protein Conformation; D018343:Receptors, Adrenergic, beta-2 / Q000737:chemistry*
chemical_list: D018343:Receptors, Adrenergic, beta-2; D020962:Heterotrimeric GTP-Binding Proteins