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- PDB-9nx2: Muscle-type nicotinic acetylcholine receptor bound to conotoxin ImII -

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Basic information

Entry
Database: PDB / ID: 9nx2
TitleMuscle-type nicotinic acetylcholine receptor bound to conotoxin ImII
Components
  • (Acetylcholine receptor subunit ...) x 4
  • Alpha-conotoxin ImII
KeywordsMEMBRANE PROTEIN / ion channel / toxin
Function / homology
Function and homology information


host cell postsynaptic membrane / acetylcholine receptor inhibitor activity / acetylcholine-gated monoatomic cation-selective channel activity / ion channel regulator activity / transmitter-gated monoatomic ion channel activity involved in regulation of postsynaptic membrane potential / transmembrane signaling receptor activity / toxin activity / postsynaptic membrane / extracellular region
Similarity search - Function
Alpha-conotoxin family signature. / Nicotinic acetylcholine receptor / Neurotransmitter-gated ion-channel, conserved site / Neurotransmitter-gated ion-channels signature. / Neurotransmitter-gated ion-channel transmembrane domain / Neurotransmitter-gated ion-channel transmembrane region / Neurotransmitter-gated ion-channel transmembrane domain superfamily / Neuronal acetylcholine receptor / Neurotransmitter-gated ion-channel / Neurotransmitter-gated ion-channel ligand-binding domain ...Alpha-conotoxin family signature. / Nicotinic acetylcholine receptor / Neurotransmitter-gated ion-channel, conserved site / Neurotransmitter-gated ion-channels signature. / Neurotransmitter-gated ion-channel transmembrane domain / Neurotransmitter-gated ion-channel transmembrane region / Neurotransmitter-gated ion-channel transmembrane domain superfamily / Neuronal acetylcholine receptor / Neurotransmitter-gated ion-channel / Neurotransmitter-gated ion-channel ligand-binding domain / Neurotransmitter-gated ion-channel ligand-binding domain superfamily / Neurotransmitter-gated ion-channel ligand binding domain
Similarity search - Domain/homology
Chem-CCE / Acetylcholine receptor subunit alpha / Acetylcholine receptor subunit beta / Acetylcholine receptor subunit gamma / Acetylcholine receptor subunit delta / Alpha-conotoxin ImII
Similarity search - Component
Biological speciesTetronarce californica (Pacific electric ray)
Conus imperialis (invertebrata)
MethodELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 2.96 Å
AuthorsStowell, M.H.B. / Hibbs, R.E. / Noviello, C.M. / Bhattacharjee, B.
Funding support United States, 3items
OrganizationGrant numberCountry
National Institutes of Health/National Institute of Neurological Disorders and Stroke (NIH/NINDS)NS120496 United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)U24GM129547 United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)GM136430 United States
CitationJournal: Structure / Year: 2025
Title: Shape-shifting conotoxins reveal divergent pore-targeting mechanisms in nicotinic receptors.
Authors: Biddut Bhattacharjee / Colleen M Noviello / Md Mahfuzur Rahman / John P Mayer / Joanna Gajewiak / J Michael McIntosh / Ryan E Hibbs / Michael H B Stowell /
Abstract: The neuronal α7 nicotinic acetylcholine receptor (α7-nAChR) and muscle-type nicotinic acetylcholine receptor (mt-nAChR) are pivotal in synaptic signaling within the brain and the neuromuscular ...The neuronal α7 nicotinic acetylcholine receptor (α7-nAChR) and muscle-type nicotinic acetylcholine receptor (mt-nAChR) are pivotal in synaptic signaling within the brain and the neuromuscular junction respectively. Additionally, they are both targets of a wide range of drugs and toxins. Here, we utilize cryo-EM to delineate structures of these nAChRs in complex with the conotoxins ImI and ImII from Conus imperialis. Despite nominal sequence differences, ImI and ImII exhibit discrete binding preferences and adopt drastically different conformational states upon binding. ImI engages the orthosteric sites of α7-nAChR, while ImII forms distinct pore-bound complexes with both α7-nAChR and mt-nAChR. Strikingly, ImII adopts a compact globular conformation that binds as a monomer to the α7-nAChR pore and as an oblate dimer to the mt-nAChR pore. These structures advance our understanding of nAChR-ligand interactions and the subtle sequence variations that result in dramatically altered functional outcomes in small peptide toxins.
History
DepositionMar 25, 2025Deposition site: RCSB / Processing site: RCSB
Revision 1.0Feb 4, 2026Provider: repository / Type: Initial release
Revision 1.0Feb 4, 2026Data content type: EM metadata / Data content type: EM metadata / Provider: repository / Type: Initial release
Revision 1.0Feb 4, 2026Data content type: FSC / Data content type: FSC / Provider: repository / Type: Initial release
Revision 1.0Feb 4, 2026Data content type: Half map / Part number: 1 / Data content type: Half map / Provider: repository / Type: Initial release
Revision 1.0Feb 4, 2026Data content type: Half map / Part number: 2 / Data content type: Half map / Provider: repository / Type: Initial release
Revision 1.0Feb 4, 2026Data content type: Image / Data content type: Image / Provider: repository / Type: Initial release
Revision 1.0Feb 4, 2026Data content type: Primary map / Data content type: Primary map / Provider: repository / Type: Initial release

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Structure visualization

Structure viewerMolecule:
MolmilJmol/JSmol

Downloads & links

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Assembly

Deposited unit
A: Acetylcholine receptor subunit alpha
B: Acetylcholine receptor subunit delta
C: Acetylcholine receptor subunit beta
D: Acetylcholine receptor subunit alpha
E: Acetylcholine receptor subunit gamma
F: Alpha-conotoxin ImII
G: Alpha-conotoxin ImII
hetero molecules


Theoretical massNumber of molelcules
Total (without water)275,85017
Polymers270,2967
Non-polymers5,55310
Water905
1


  • Idetical with deposited unit
  • defined by author&software
  • Evidence: electron microscopy, not applicable
TypeNameSymmetry operationNumber
identity operation1_555x,y,z1

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Components

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Acetylcholine receptor subunit ... , 4 types, 5 molecules ADBCE

#1: Protein Acetylcholine receptor subunit alpha


Mass: 49869.895 Da / Num. of mol.: 2 / Source method: isolated from a natural source
Source: (natural) Tetronarce californica (Pacific electric ray)
References: UniProt: P02710
#2: Protein Acetylcholine receptor subunit delta


Mass: 57455.500 Da / Num. of mol.: 1 / Source method: isolated from a natural source
Source: (natural) Tetronarce californica (Pacific electric ray)
References: UniProt: P02718
#3: Protein Acetylcholine receptor subunit beta


Mass: 53731.773 Da / Num. of mol.: 1 / Source method: isolated from a natural source
Source: (natural) Tetronarce californica (Pacific electric ray)
References: UniProt: P02712
#4: Protein Acetylcholine receptor subunit gamma


Mass: 56335.684 Da / Num. of mol.: 1 / Source method: isolated from a natural source
Source: (natural) Tetronarce californica (Pacific electric ray)
References: UniProt: P02714

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Protein/peptide , 1 types, 2 molecules FG

#5: Protein/peptide Alpha-conotoxin ImII / Alpha-CTx ImII


Mass: 1516.822 Da / Num. of mol.: 2 / Fragment: residues 5-16 / Source method: obtained synthetically / Source: (synth.) Conus imperialis (invertebrata) / References: UniProt: Q8I6R5

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Sugars , 6 types, 8 molecules

#6: Polysaccharide alpha-D-mannopyranose-(1-6)-alpha-D-mannopyranose-(1-6)-beta-D-mannopyranose-(1-4)-2-acetamido-2- ...alpha-D-mannopyranose-(1-6)-alpha-D-mannopyranose-(1-6)-beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose


Type: oligosaccharide / Mass: 910.823 Da / Num. of mol.: 2 / Source method: isolated from a natural source
DescriptorTypeProgram
DManpa1-6DManpa1-6DManpb1-4DGlcpNAcb1-4DGlcpNAcb1-ROHGlycam Condensed SequenceGMML 1.0
WURCS=2.0/3,5,4/[a2122h-1b_1-5_2*NCC/3=O][a1122h-1b_1-5][a1122h-1a_1-5]/1-1-2-3-3/a4-b1_b4-c1_c6-d1_d6-e1WURCSPDB2Glycan 1.1.0
[][D-1-deoxy-GlcpNAc]{[(4+1)][b-D-GlcpNAc]{[(4+1)][b-D-Manp]{[(6+1)][a-D-Manp]{[(6+1)][a-D-Manp]{}}}}}LINUCSPDB-CARE
#7: Polysaccharide alpha-D-mannopyranose-(1-6)-beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1- ...alpha-D-mannopyranose-(1-6)-beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose


Type: oligosaccharide / Mass: 748.682 Da / Num. of mol.: 1 / Source method: isolated from a natural source
DescriptorTypeProgram
DManpa1-6DManpb1-4DGlcpNAcb1-4DGlcpNAcb1-ROHGlycam Condensed SequenceGMML 1.0
WURCS=2.0/3,4,3/[a2122h-1b_1-5_2*NCC/3=O][a1122h-1b_1-5][a1122h-1a_1-5]/1-1-2-3/a4-b1_b4-c1_c6-d1WURCSPDB2Glycan 1.1.0
[][D-1-deoxy-GlcpNAc]{[(4+1)][b-D-GlcpNAc]{[(4+1)][b-D-Manp]{[(6+1)][a-D-Manp]{}}}}LINUCSPDB-CARE
#8: Polysaccharide 2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose


Type: oligosaccharide / Mass: 424.401 Da / Num. of mol.: 1 / Source method: isolated from a natural source
DescriptorTypeProgram
DGlcpNAcb1-4DGlcpNAcb1-ROHGlycam Condensed SequenceGMML 1.0
WURCS=2.0/1,2,1/[a2122h-1b_1-5_2*NCC/3=O]/1-1/a4-b1WURCSPDB2Glycan 1.1.0
[][D-1-deoxy-GlcpNAc]{[(4+1)][b-D-GlcpNAc]{}}LINUCSPDB-CARE
#9: Polysaccharide beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta- ...beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose


Type: oligosaccharide / Mass: 586.542 Da / Num. of mol.: 1 / Source method: isolated from a natural source
DescriptorTypeProgram
DManpb1-4DGlcpNAcb1-4DGlcpNAcb1-ROHGlycam Condensed SequenceGMML 1.0
WURCS=2.0/2,3,2/[a2122h-1b_1-5_2*NCC/3=O][a1122h-1b_1-5]/1-1-2/a4-b1_b4-c1WURCSPDB2Glycan 1.1.0
[][D-1-deoxy-GlcpNAc]{[(4+1)][b-D-GlcpNAc]{[(4+1)][b-D-Manp]{}}}LINUCSPDB-CARE
#10: Polysaccharide alpha-D-mannopyranose-(1-2)-[alpha-D-mannopyranose-(1-6)]alpha-D-mannopyranose-(1-6)-[alpha-D- ...alpha-D-mannopyranose-(1-2)-[alpha-D-mannopyranose-(1-6)]alpha-D-mannopyranose-(1-6)-[alpha-D-mannopyranose-(1-3)]beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose


Type: oligosaccharide / Mass: 1235.105 Da / Num. of mol.: 1 / Source method: isolated from a natural source
DescriptorTypeProgram
DManpa1-2[DManpa1-6]DManpa1-6[DManpa1-3]DManpb1-4DGlcpNAcb1-4DGlcpNAcb1-ROHGlycam Condensed SequenceGMML 1.0
WURCS=2.0/3,7,6/[a2122h-1b_1-5_2*NCC/3=O][a1122h-1b_1-5][a1122h-1a_1-5]/1-1-2-3-3-3-3/a4-b1_b4-c1_c3-d1_c6-e1_e2-f1_e6-g1WURCSPDB2Glycan 1.1.0
[][D-1-deoxy-GlcpNAc]{[(4+1)][b-D-GlcpNAc]{[(4+1)][b-D-Manp]{[(3+1)][a-D-Manp]{}[(6+1)][a-D-Manp]{[(2+1)][a-D-Manp]{}[(6+1)][a-D-Manp]{}}}}}LINUCSPDB-CARE
#12: Sugar ChemComp-NAG / 2-acetamido-2-deoxy-beta-D-glucopyranose / N-acetyl-beta-D-glucosamine / 2-acetamido-2-deoxy-beta-D-glucose / 2-acetamido-2-deoxy-D-glucose / 2-acetamido-2-deoxy-glucose / N-ACETYL-D-GLUCOSAMINE


Type: D-saccharide, beta linking / Mass: 221.208 Da / Num. of mol.: 2 / Source method: obtained synthetically / Formula: C8H15NO6
IdentifierTypeProgram
DGlcpNAcbCONDENSED IUPAC CARBOHYDRATE SYMBOLGMML 1.0
N-acetyl-b-D-glucopyranosamineCOMMON NAMEGMML 1.0
b-D-GlcpNAcIUPAC CARBOHYDRATE SYMBOLPDB-CARE 1.0
GlcNAcSNFG CARBOHYDRATE SYMBOLGMML 1.0

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Non-polymers , 2 types, 7 molecules

#11: Chemical ChemComp-CCE / 2-[(AMINOCARBONYL)OXY]-N,N,N-TRIMETHYLETHANAMINIUM / CARBAMYL-CHOLINE


Mass: 147.195 Da / Num. of mol.: 2 / Source method: obtained synthetically / Formula: C6H15N2O2
#13: Water ChemComp-HOH / water


Mass: 18.015 Da / Num. of mol.: 5 / Source method: isolated from a natural source / Formula: H2O

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Details

Has ligand of interestN
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

Component
IDNameTypeEntity IDParent-IDSource
1Complex of conotoxin ImII and human muscle-type nicotinic acetyclcholine receptorCOMPLEX#1-#50MULTIPLE SOURCES
2Human muscle-type nicotinic acetyclcholine receptorCOMPLEX#1-#41NATURAL
3Conotoxin ImIICOMPLEX#51SYNTHETIC
Molecular weightExperimental value: NO
Source (natural)
IDEntity assembly-IDOrganismNcbi tax-ID
22Tetronarce californica (Pacific electric ray)7787
33Conus imperialis (invertebrata)35631
Buffer solutionpH: 7.4
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: 30000 nm / Nominal defocus min: 5000 nm / Calibrated defocus min: 5000 nm / Cs: 2.7 mm
Image recordingElectron dose: 50 e/Å2 / Detector mode: SUPER-RESOLUTION / Film or detector model: GATAN K2 SUMMIT (4k x 4k)

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Processing

EM software
IDNameVersionCategory
7Cootmodel fitting
9PHENIX1.20.1_4487model refinement
13cryoSPARC3D reconstruction
CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
3D reconstructionResolution: 2.96 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 128448 / Symmetry type: POINT
Atomic model buildingProtocol: FLEXIBLE FIT
Atomic model buildingPDB-ID: 7KOO

7koo


Accession code: 7KOO / Source name: PDB / Type: experimental model
RefinementHighest resolution: 2.96 Å
Stereochemistry target values: REAL-SPACE (WEIGHTED MAP SUM AT ATOM CENTERS)
Refine LS restraints
Refine-IDTypeDev idealNumber
ELECTRON MICROSCOPYf_bond_d0.00317547
ELECTRON MICROSCOPYf_angle_d0.46923938
ELECTRON MICROSCOPYf_dihedral_angle_d10.816451
ELECTRON MICROSCOPYf_chiral_restr0.0422842
ELECTRON MICROSCOPYf_plane_restr0.0042935

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