期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 284, 期 39, 页码 26732-26741出版社
ELSEVIER
DOI: 10.1074/jbc.M109.026922
关键词
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资金
- National Institutes of Health [GM068603, GM07767, GM081025, P60-DK020572]
- Michigan Diabetes Research and Training Center
Despite extensive characterization of the mu-opioid receptor (MOR), the biochemical properties of the isolated receptor remain unclear. In light of recent reports, we proposed that the monomeric form of MOR can activate G proteins and be subject to allosteric regulation. A mu-opioid receptor fused to yellow fluorescent protein (YMOR) was constructed and expressed in insect cells. YMOR binds ligands with high affinity, displays agonist-stimulated [S-35]guanosine 5'-(gamma-thio)triphosphate binding to G alpha(i), and is allosterically regulated by coupled G(i) protein heterotrimer both in insect cell membranes and as purified protein reconstituted into a phospholipid bilayer in the form of high density lipoprotein particles. Single-particle imaging of fluorescently labeled receptor indicates that the reconstituted YMOR is monomeric. Moreover, single-molecule imaging of a Cy3-labeled agonist, [Lys(7), Cys(8)]dermorphin, illustrates a novel method for studying G protein-coupled receptor-ligand binding and suggests that one molecule of agonist binds per monomeric YMOR. Together these data support the notion that oligomerization of the mu-opioid receptor is not required for agonist and antagonist binding and that the monomeric receptor is the minimal functional unit in regard to G protein activation and strong allosteric regulation of agonist binding by G proteins.
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