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EMBO J. 2006 Dec 13;25(24):5693-702. Epub 2006 Nov 30.

Asymmetric conformational changes in a GPCR dimer controlled by G-proteins.

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UMR 5074 CNRS, Laboratoire de Chimie Biomoléculaire et Interactions Biologiques, Faculté de Pharmacie, 17 Avenue Ch. Flahault, 34093 Montpellier Cedex 5, France.


G-protein-coupled receptors (GPCRs) are key players in cell communication. Although long considered as monomeric, it now appears that these heptahelical proteins can form homo- or heterodimers. Here, we analyzed the conformational changes in each subunit of a receptor dimer resulting from agonist binding to either one or both subunits by measuring the fluorescent properties of a leukotriene B(4) receptor dimer with a single 5-hydroxytryptophan-labeled protomer. We show that a receptor dimer with only a single agonist-occupied subunit can trigger G-protein activation. We also show that the two subunits of the receptor dimer in the G-protein-coupled state differ in their conformation, even when both are liganded by the agonist. No such asymmetric conformational changes are observed in the absence of G-protein, indicating that the interaction of the G-protein with the receptor dimer brings specific constraints that prevent a symmetric functioning of this dimer. These data open new options for the differential signaling properties of GPCR dimers.

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