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Ligand‐regulated oligomerization of β 2 ‐adrenoceptors in a model lipid bilayer
Author(s) -
Fung Juan José,
Deupi Xavier,
Pardo Leonardo,
Yao Xiao Jie,
VelezRuiz Gisselle A,
DeVree Brian T,
Sunahara Roger K,
Kobilka Brian K
Publication year - 2009
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2009.267
Subject(s) - biology , ligand (biochemistry) , lipid bilayer , biophysics , receptor , microbiology and biotechnology , biochemistry , membrane
The β 2 ‐adrenoceptor (β 2 AR) was one of the first Family A G protein‐coupled receptors (GPCRs) shown to form oligomers in cellular membranes, yet we still know little about the number and arrangement of protomers in oligomers, the influence of ligands on the organization or stability of oligomers, or the requirement for other proteins to promote oligomerization. We used fluorescence resonance energy transfer (FRET) to characterize the oligomerization of purified β 2 AR site‐specifically labelled at three different positions with fluorophores and reconstituted into a model lipid bilayer. Our results suggest that the β 2 AR is predominantly tetrameric following reconstitution into phospholipid vesicles. Agonists and antagonists have little effect on the relative orientation of protomers in oligomeric complexes. In contrast, binding of inverse agonists leads to significant increases in FRET efficiencies for most labelling pairs, suggesting that this class of ligand promotes tighter packing of protomers and/or the formation of more complex oligomers by reducing conformational fluctuations in individual protomers. The results provide new structural insights into β 2 AR oligomerization and suggest a possible mechanism for the functional effects of inverse agonists.