Publication Date:
2015-08-08
Description:
micro-Opioid receptors (microORs) are G-protein-coupled receptors that are activated by a structurally diverse spectrum of natural and synthetic agonists including endogenous endorphin peptides, morphine and methadone. The recent structures of the muOR in inactive and agonist-induced active states (Huang et al., ref. 2) provide snapshots of the receptor at the beginning and end of a signalling event, but little is known about the dynamic sequence of events that span these two states. Here we use solution-state NMR to examine the process of muOR activation using a purified receptor (mouse sequence) preparation in an amphiphile membrane-like environment. We obtain spectra of the muOR in the absence of ligand, and in the presence of the high-affinity agonist BU72 alone, or with BU72 and a G protein mimetic nanobody. Our results show that conformational changes in transmembrane segments 5 and 6 (TM5 and TM6), which are required for the full engagement of a G protein, are almost completely dependent on the presence of both the agonist and the G protein mimetic nanobody, revealing a weak allosteric coupling between the agonist-binding pocket and the G-protein-coupling interface (TM5 and TM6), similar to that observed for the beta2-adrenergic receptor. Unexpectedly, in the presence of agonist alone, we find larger spectral changes involving intracellular loop 1 and helix 8 compared to changes in TM5 and TM6. These results suggest that one or both of these domains may play a role in the initial interaction with the G protein, and that TM5 and TM6 are only engaged later in the process of complex formation. The initial interactions between the G protein and intracellular loop 1 and/or helix 8 may be involved in G-protein coupling specificity, as has been suggested for other family A G-protein-coupled receptors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sounier, Remy -- Mas, Camille -- Steyaert, Jan -- Laeremans, Toon -- Manglik, Aashish -- Huang, Weijiao -- Kobilka, Brian K -- Demene, Helene -- Granier, Sebastien -- DA036246/DA/NIDA NIH HHS/ -- R37 DA036246/DA/NIDA NIH HHS/ -- T32 GM008294/GM/NIGMS NIH HHS/ -- England -- Nature. 2015 Aug 20;524(7565):375-8. doi: 10.1038/nature14680. Epub 2015 Aug 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut de Genomique Fonctionnelle, CNRS UMR-5203 INSERM U1191, University of Montpellier, F-34000 Montpellier, France. ; Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium. ; Structural Biology Research Center, VIB, Pleinlaan 2, B-1050 Brussels, Belgium. ; Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA. ; Centre de Biochimie Structurale, CNRS UMR 5048-INSERM 1054- University of Montpellier, 29 rue de Navacelles, 34090 Montpellier Cedex, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26245377" target="_blank"〉PubMed〈/a〉
Keywords:
Allosteric Regulation
;
Animals
;
Binding Sites
;
Heterotrimeric GTP-Binding Proteins/metabolism
;
Lysine/metabolism
;
Mice
;
Models, Molecular
;
Morphinans/chemistry/metabolism/pharmacology
;
Nuclear Magnetic Resonance, Biomolecular
;
Protein Binding
;
Protein Conformation/drug effects
;
Pyrroles/chemistry/metabolism/pharmacology
;
Receptors, Adrenergic, beta-2/chemistry
;
Receptors, Opioid, mu/*chemistry/*metabolism
;
Single-Chain Antibodies/chemistry/metabolism/pharmacology
;
Structure-Activity Relationship
;
Substrate Specificity
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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