α-Conotoxin MI is a 14-amino-acid disulfide-rich peptide originally characterized from the fish-hunting cone snail Conus magus. It is a classical α3/5 conotoxin that competitively inhibits muscle-type nicotinic acetylcholine receptors at the neuromuscular junction.

Its short, conformationally constrained structure has made MI an established molecular probe for studying ligand-binding interfaces, neuromuscular nAChR pharmacology, and the structural determinants governing α-conotoxin recognition.

Product Information

The sequence and native fold contain four cysteine residues forming two disulfide bonds, not three disulfide bridges.

Muscle nAChR Pharmacology

MI interacts with the extracellular ligand-binding region of muscle nicotinic receptors and competes with acetylcholine for receptor activation.

Studies of muscle nAChRs have shown that MI can distinguish between agonist-binding interfaces and that the observed preference changes with receptor species and subunit composition. These differences are particularly useful when studying the α/γ and α/δ interfaces of neuromuscular receptors.

Why MI Is Useful for Structure–Function Studies

The compact scaffold allows individual residues to be evaluated without the complexity of a large protein ligand. Comparison of MI with closely related GI, SI, and SIA demonstrates how changes within a short peptide sequence can substantially affect receptor recognition.

This makes MI suitable for peptide analog design, receptor-interface mapping, and comparative conotoxin SAR.

Sequence and Molecular Form

The mature sequence is:

GRCCHPACGKNYSC-NH₂

The native globular fold contains two disulfide bonds, Cys3–Cys8 and Cys4–Cys14, together with a C-terminal amide.

For experiments relying on receptor activity, We recommend considering correct folding and molecular identity together with chromatographic purity.

Custom MI analogs, residue substitutions, and related disulfide-rich sequences can be discussed through Custom Peptide Synthesis.

Quality and Procurement Considerations

For lab managers planning electrophysiology or receptor-binding studies, the required quantity, purity, and analytical documentation should be established before scheduling the assay.

MS and analytical HPLC provide complementary information on identity and chromatographic purity. Additional guidance on selecting a fit-for-purpose specification is available in Recommended Peptide Purity.

For comparison with other ion-channel and receptor probes, see Bioactive Toxin-Derived Peptides.

Storage and Handling

Store the lyophilized material under the conditions specified for the supplied batch. Following reconstitution, use handling and aliquoting conditions appropriate to the solvent, concentration, and experimental workflow.

Research Use Only

α-Conotoxin MI is supplied for research use only. It is not intended for therapeutic, or human use.