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Alpha-conotoxin ImI

Conus imperialis (Imperial cone)
Reviewed-Annotation score: -Experimental evidence at protein leveli


Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. This toxin blocks neuronal alpha-3/beta-2 (human and rat), alpha-7 (human and rat), and alpha-3/beta-4 (human) nAChRs (PubMed:8206995, PubMed:15609996, PubMed:19131337). Acts voltage-independently (PubMed:15609996). Competes with alpha-bungarotoxin for binding to the receptor (PubMed:12384509, PubMed:15609996). Binds to a different site than alpha-conotoxin ImII (PubMed:15609996). Is highly active against the neuromuscular receptor in frog (PubMed:8206995).4 Publications


This toxin is a substrate for a multienzyme complex that regulates its folding and assembly. This complex is composed of protein-disulfide isomerase (PDI), peptidyl-prolyl cis-trans isomerase (PPI) and immunoglobulin-binding protein (BiP). PDI catalyzes the oxidation and reduction of disulfide bonds. Oxidative folding rates are further increased in the presence of PPI with the maximum effect observed in the presence of both enzymes. In contrast, BiP is only observed to assist folding in the presence of microsomes, suggesting that additional cofactors are involved. This toxin has been observed in the venom as globular (disulfide pattern C1-C3 and C2-C4) and ribbon form (C1-C4 and C2-C3).1 Publication
Does not inhibit alpha-2-beta-2, alpha-4-beta-2, alpha-2-beta-4, alpha-3-beta-4, and alpha-4-beta-4 subunits (PubMed:7651351, PubMed:15609996). Has also no effect on muscle nAChRs alpha-1-beta-1-delta-epsilon (PubMed:15609996).2 Publications


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sitei9Important for binding to human alpha-7 nAChR1 Publication1
Sitei10Important for binding to human alpha-7 nAChR1 Publication1
Sitei11Important for binding to human alpha-7 nAChR1 Publication1
Sitei13Important for binding to human alpha-7 nAChR1 Publication1
Sitei14Important for binding to human alpha-7 nAChR1 Publication1

GO - Molecular functioni


Molecular functionAcetylcholine receptor inhibiting toxin, Ion channel impairing toxin, Neurotoxin, Postsynaptic neurotoxin, Toxin

Names & Taxonomyi

Protein namesi
Recommended name:
Alpha-conotoxin ImI2 Publications
Short name:
Alpha-CTx ImI1 Publication
OrganismiConus imperialis (Imperial cone)
Taxonomic identifieri35631 [NCBI]
Taxonomic lineageiEukaryotaMetazoaLophotrochozoaMolluscaGastropodaCaenogastropodaHypsogastropodaNeogastropodaConoideaConidaeConusStephanoconus

Organism-specific databases

ConoServeri93 ImI precursor

Subcellular locationi

Extracellular region or secreted Cytosol Plasma membrane Cytoskeleton Lysosome Endosome Peroxisome ER Golgi apparatus Nucleus Mitochondrion Manual annotation Automatic computational assertionGraphics by Christian Stolte; Source: COMPARTMENTS

Keywords - Cellular componenti


Pathology & Biotechi


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Mutagenesisi9D → L: Reduction of toxicity. 1 Publication1
Mutagenesisi10P → R: Loss of ability to compete with alpha-bungarotoxin. 1 Publication1
Mutagenesisi11R → L: Reduction of toxicity. 1 Publication1
Mutagenesisi15R → E: No loss of activity. 1 Publication1

PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
PropeptideiPRO_0000273426‹1 – 41 Publication›4
PeptideiPRO_00000348775 – 16Alpha-conotoxin ImI1 PublicationAdd BLAST12

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Disulfide bondi6 ↔ 16In Imi-ribbon form; alternate1 Publication
Disulfide bondi6 ↔ 12In Imi-globular form; alternate6 Publications
Disulfide bondi7 ↔ 16In Imi-globular form; alternate6 Publications
Disulfide bondi7 ↔ 12In Imi-ribbon form; alternate1 Publication
Modified residuei16Cysteine amide1 Publication1

Post-translational modificationi

Not hydroxylated; hydroxylation improves its folding but impairs its activity against target receptors.1 Publication

Keywords - PTMi

Amidation, Cleavage on pair of basic residues, Disulfide bond


Tissue specificityi

Expressed by the venom duct.Curated


Protein-protein interaction databases

IntActiP50983, 1 interactor


Secondary structure

Legend: HelixTurnBeta strandPDB Structure known for this area
Show more details
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Helixi6 – 8Combined sources3
Turni10 – 12Combined sources3
Helixi13 – 15Combined sources3

3D structure databases


Miscellaneous databases


Family & Domainsi


The cysteine framework is I (CC-C-C). Alpha4/3 pattern.Curated

Sequence similaritiesi

Belongs to the conotoxin A superfamily.Curated

Family and domain databases

InterProiView protein in InterPro
IPR018072 Conotoxin_a-typ_CS
PROSITEiView protein in PROSITE


Sequence statusi: Fragment.

Sequence processingi: The displayed sequence is further processed into a mature form.

Mass (Da):1,938
Last modified:January 16, 2004 - v2

Experimental Info

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Non-terminal residuei11

Mass spectrometryi

Molecular mass is 1351.48 Da from positions 5 - 16. Monoisotopic mass.1 Publication

Sequence databases

Select the link destinations:
Links Updated
AY159318 Genomic DNA Translation: AAN78128.1

Similar proteinsi

Entry informationi

Entry nameiCA1_CONIM
AccessioniPrimary (citable) accession number: P50983
Secondary accession number(s): Q8I6R4
Entry historyiIntegrated into UniProtKB/Swiss-Prot: October 1, 1996
Last sequence update: January 16, 2004
Last modified: January 31, 2018
This is version 98 of the entry and version 2 of the sequence. See complete history.
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programAnimal Toxin Annotation Program


Keywords - Technical termi

3D-structure, Direct protein sequencing


  1. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  2. SIMILARITY comments
    Index of protein domains and families

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