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- PDB-9mbb: Cryo-EM structure of antagonist-bound GPCR -

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Basic information

Entry
Database: PDB / ID: 9mbb
TitleCryo-EM structure of antagonist-bound GPCR
ComponentsMetabotropic glutamate receptor 8
KeywordsMEMBRANE PROTEIN / Antagonist
Function / homology
Function and homology information


group III metabotropic glutamate receptor activity / adenylate cyclase-inhibiting G protein-coupled glutamate receptor signaling pathway / G protein-coupled glutamate receptor signaling pathway / Class C/3 (Metabotropic glutamate/pheromone receptors) / glutamate receptor activity / regulation of synaptic transmission, glutamatergic / visual perception / G protein-coupled receptor activity / adenylate cyclase-inhibiting G protein-coupled receptor signaling pathway / G alpha (i) signalling events / plasma membrane
Similarity search - Function
GPCR, family 3, metabotropic glutamate receptor 8 / GPCR, family 3, metabotropic glutamate receptor / : / G-protein coupled receptors family 3 signature 1. / G-protein coupled receptors family 3 signature 3. / G-protein coupled receptors family 3 signature 2. / GPCR, family 3, nine cysteines domain / GPCR, family 3, nine cysteines domain superfamily / Nine Cysteines Domain of family 3 GPCR / GPCR, family 3, conserved site ...GPCR, family 3, metabotropic glutamate receptor 8 / GPCR, family 3, metabotropic glutamate receptor / : / G-protein coupled receptors family 3 signature 1. / G-protein coupled receptors family 3 signature 3. / G-protein coupled receptors family 3 signature 2. / GPCR, family 3, nine cysteines domain / GPCR, family 3, nine cysteines domain superfamily / Nine Cysteines Domain of family 3 GPCR / GPCR, family 3, conserved site / GPCR, family 3 / G-protein coupled receptors family 3 profile. / GPCR family 3, C-terminal / 7 transmembrane sweet-taste receptor of 3 GCPR / Receptor, ligand binding region / Receptor family ligand binding region / Periplasmic binding protein-like I
Similarity search - Domain/homology
Chem-Z99 / Metabotropic glutamate receptor 8
Similarity search - Component
Biological speciesHomo sapiens (human)
MethodELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 3.25 Å
AuthorsZhao, J. / Zhao, C. / Sun, H. / Shao, Z.H.
Funding support1items
OrganizationGrant numberCountry
Not funded
CitationJournal: Mol Cell / Year: 2025
Title: Structural characterization of five functional states of metabotropic glutamate receptor 8.
Authors: Jie Zhao / Yue Deng / Zheng Xu / Chanjuan Xu / Chang Zhao / Ziyan Li / Hui Sun / Xiaowen Tian / Yuxuan Song / Marta Cimadevila / Heli Wang / Yuxuan Liu / Xiaoyu Zhang / Yiyang Chen / Suyue ...Authors: Jie Zhao / Yue Deng / Zheng Xu / Chanjuan Xu / Chang Zhao / Ziyan Li / Hui Sun / Xiaowen Tian / Yuxuan Song / Marta Cimadevila / Heli Wang / Yuxuan Liu / Xiaoyu Zhang / Yiyang Chen / Suyue Sun / Xihao Yong / Lantian Su / Yixiao He / Yi Zhong / Hao Yang / Jean-Philippe Pin / Wei Yan / Zhenhua Shao / Jianfeng Liu /
Abstract: Metabotropic glutamate receptors (mGluRs) are dimeric class C G protein-coupled receptors, which play crucial roles in brain physiology and pathology. Among them, mGlu8 is the least characterized, ...Metabotropic glutamate receptors (mGluRs) are dimeric class C G protein-coupled receptors, which play crucial roles in brain physiology and pathology. Among them, mGlu8 is the least characterized, though it is physiologically important. While recognized to signal via G proteins, the involvement of β-arrestin is unknown. Here, we found that both mGlu8 agonists and positive allosteric modulators (PAMs) activate G signaling, but mainly agonists induce β-arrestin recruitment. We solved five human mGlu8 cryo-electron microscopy (cryo-EM) structures in various states: apo, antagonist-bound, agonist + PAM-bound, agonist + PAM-bound with G protein, and agonist-bound with β-arrestin1 states. They revealed a unique PAM-binding pocket at the extracellular side of the TM6/TM7 interface. Agonist and PAM promote active mGlu8 association with one G protein asymmetrically (2:1), while two β-arrestin1 can interact symmetrically (2:2) to both subunits of an inactive dimer state to promote constitutive internalization. These findings elucidate how mGlu8 selectively engages transducers, offering insights into its signaling capabilities and selective drug development.
History
DepositionMar 15, 2025Deposition site: PDBJ / Processing site: PDBC
Revision 1.0Oct 1, 2025Provider: repository / Type: Initial release

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Structure visualization

Structure viewerMolecule:
MolmilJmol/JSmol

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Assembly

Deposited unit
A: Metabotropic glutamate receptor 8
B: Metabotropic glutamate receptor 8
hetero molecules


Theoretical massNumber of molelcules
Total (without water)204,4244
Polymers203,7172
Non-polymers7072
Water00
1


  • Idetical with deposited unit
  • defined by author
  • Evidence: electron microscopy, not applicable
TypeNameSymmetry operationNumber
identity operation1_5551

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Components

#1: Protein Metabotropic glutamate receptor 8 / mGluR8


Mass: 101858.414 Da / Num. of mol.: 2
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Homo sapiens (human) / Gene: GRM8, GPRC1H, MGLUR8 / Production host: Spodoptera frugiperda (fall armyworm) / References: UniProt: O00222
#2: Chemical ChemComp-Z99 / 2-[(1S,2S)-2-carboxycyclopropyl]-3-(9H-xanthen-9-yl)-D-alanine / (1S,2S)-2-[(2S)-2-amino-1-hydroxy-1-oxo-3-(9H-xanthen-9-yl)propan-2-yl]cyclopropane-1-carboxylic acid


Mass: 353.369 Da / Num. of mol.: 2 / Source method: obtained synthetically / Formula: C20H19NO5 / Feature type: SUBJECT OF INVESTIGATION
Has ligand of interestY
Has protein modificationY

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Experimental details

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Experiment

ExperimentMethod: ELECTRON MICROSCOPY
EM experimentAggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction

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Sample preparation

ComponentName: GPCR bound to an antagonist / Type: COMPLEX / Entity ID: #1 / Source: RECOMBINANT
Source (natural)Organism: Homo sapiens (human)
Source (recombinant)Organism: Spodoptera frugiperda (fall armyworm)
Buffer solutionpH: 7.5
SpecimenEmbedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
VitrificationCryogen name: ETHANE

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Electron microscopy imaging

Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
MicroscopyModel: TFS KRIOS
Electron gunElectron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: FLOOD BEAM
Electron lensMode: BRIGHT FIELD / Nominal defocus max: 1200 nm / Nominal defocus min: 600 nm / Cs: 2.7 mm
Image recordingElectron dose: 50 e/Å2 / Film or detector model: TFS FALCON 4i (4k x 4k)

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Processing

EM software
IDNameCategory
1cryoSPARCparticle selection
8PHENIXmodel refinement
13Coot3D reconstruction
CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
3D reconstructionResolution: 3.25 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 121664 / Symmetry type: POINT

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