期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 104, 期 18, 页码 7682-7687出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0611448104
关键词
beta(2)-adrenergic receptor; single-molecule spectroscopy; oligomerization
资金
- NIDDK NIH HHS [P60 DK020572, P60DK-20572] Funding Source: Medline
- NIGMS NIH HHS [R01 GM068603, GM068603] Funding Source: Medline
- NINDS NIH HHS [R01 NS028471, R37 NS028471, NS28471] Funding Source: Medline
G protein-coupled receptors (GPCRs) respond to a diverse array of ligands, mediating cellular responses to hormones and neurotransmitters, as well as the senses of smell and taste. The structures of the GPCR rhodopsin and several G proteins have been determined by x-ray crystallography, yet the organization of the signaling complex between GPCRs and G proteins is poorly understood. The observations that some GPCRs are obligate heterodimers, and that many GPCRs form both homo- and heterodimers, has led to speculation that GPCR climers may be required for efficient activation of G proteins. However, technical limitations have precluded a definitive analysis of G protein coupling to monomeric GPCRs in a biochemically defined and membrane-bound system. Here we demonstrate that a prototypical GPCR, the beta(2)-adrenergic receptor (beta(2)AR), can be incorporated into a reconstituted high-density lipoprotein (rHDL) phospholipid bilayer particle together with the stimulatory heterotrimeric G protein, Gs. Single-molecule fluorescence imaging and FRET analysis demonstrate that a single beta(2)AR is incorporated per rHDL particle. The monomeric beta(2)AR efficiently activates Gs and displays GTP-sensitive allosteric ligand-binding properties. These data suggest that a monomeric receptor in a lipid bilayer is the minimal functional unit necessary for signaling, and that the cooperativity of agonist binding is due to G protein association with a receptor monomer and not receptor oligomerization.
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