Apamin is an 18-amino-acid disulfide-rich peptide originally identified in honeybee (Apis mellifera) venom. It is widely used as a pharmacological probe for small-conductance Ca²⁺-activated K⁺ channels (KCa2/SK channels), with particularly high sensitivity reported for KCa2.2/SK2 encoded by KCNN2.

Its defined sequence, two intramolecular disulfide bonds, and C-terminal amidation give Apamin a compact molecular structure that is important to its biological activity. These properties make AS2618 relevant to electrophysiology, neuronal excitability studies, ion-channel pharmacology, calcium-dependent signaling, and structure–activity research.

Product Information

Apamin belongs to a broader group of structurally defined bioactive toxin-derived peptides used as molecular probes in receptor, ion-channel, signaling, and neurobiology research.

Biological Target and Activity

Apamin inhibits small-conductance calcium-activated potassium channels in a subtype-dependent manner. KCa2.2/SK2 generally displays the highest reported sensitivity, while KCa2.3/SK3 and KCa2.1/SK1 respond at higher concentrations.

Reported potency can vary with species, channel construct, expression system, membrane potential, and assay conditions. These ranges should therefore be considered literature references rather than batch-specific activity specifications.

Role in SK Channel Studies

KCa2 channels couple intracellular calcium signals to potassium conductance and contribute to membrane hyperpolarization. In neuronal systems, they are involved in afterhyperpolarization, firing patterns, and the regulation of excitability.

Apamin is frequently used in electrophysiological experiments to help identify the contribution of SK-mediated currents and to distinguish these responses from other potassium-channel activity. The high sensitivity of SK2 to this molecule has made it an established tool in both native-cell and heterologous expression studies.

Sequence and Disulfide Architecture

The mature sequence is:

CNCKAPETALCARRCQQH-NH₂

The four cysteine residues form two intramolecular disulfide bonds:

Cys1–Cys11
Cys3–Cys15

The C-terminal histidine is amidated.

For a peptide with this architecture, sequence alone does not fully describe the intended molecular form. Correct oxidation and disulfide formation should be considered together with molecular identity and chromatographic purity when material is intended for functional research.

This consideration is particularly relevant when producing Apamin analogs or variants containing amino-acid substitutions. Researchers developing related sequences can use our Custom Peptide Synthesis service for project-specific synthesis, disulfide formation, terminal modification, purity, and analytical requirements.

Research Applications

Apamin is commonly used in studies of SK/KCa2 channel function, electrophysiology, neuronal excitability, calcium-dependent potassium signaling, synaptic physiology, and peptide structure–activity relationships.

For neuroscience and ion-channel experiments, the appropriate working concentration should be determined for the specific model and assay configuration. Published potency values provide a useful starting reference, but experimental response can differ substantially between recombinant systems, isolated cells, tissues, and species.

Quality Control Considerations

For disulfide-containing peptides, chromatographic purity and molecular identity address different aspects of material quality. Analytical HPLC is used to assess chromatographic purity, while mass spectrometry supports confirmation of the expected molecular mass.

Our Peptide Quality Control capabilities support analytical characterization and batch-specific documentation for research peptides.

For assay-sensitive applications, purity requirements should be matched to the downstream experiment rather than selected solely on the basis of the highest available specification. Researchers and laboratory managers can refer to our Recommended Peptide Purity guidance when planning screening, biochemical, cell-based, or other research workflows.

Ordering and Laboratory Planning

Use AS2618 when requesting quotations, preparing purchase orders, or maintaining internal laboratory records for Apamin.

For routine research procurement, quantity, purity, analytical documentation, and expected lead time should be reviewed before an experiment is scheduled. Larger quantities, customized purity requirements, sequence variants, or modified analogs can be evaluated separately according to the intended research application.

Storage and Handling

Store lyophilized Apamin under the conditions specified for the supplied batch and protect the material from moisture and unnecessary temperature cycling.

After reconstitution, stability can depend on solvent composition, concentration, pH, temperature, and storage duration. Where appropriate, preparing single-use or experiment-sized aliquots can reduce repeated freeze–thaw exposure.

Frequently Asked Questions

What does Apamin target?

Apamin is best known as a blocker of small-conductance Ca²⁺-activated potassium channels. KCa2.2/SK2 is particularly sensitive to the peptide and is one of its most commonly studied pharmacological targets.

What is the sequence of Apamin?

The mature sequence is CNCKAPETALCARRCQQH-NH₂. It contains 18 amino acids, two intramolecular disulfide bonds, and a C-terminal amide.

Why is Apamin used in electrophysiology?

Its activity against KCa2/SK channels allows researchers to investigate the contribution of these channels to calcium-dependent potassium currents, membrane hyperpolarization, afterhyperpolarization, and neuronal excitability.

Can Apamin analogs be synthesized?

Yes. Sequence substitutions, terminal modifications, and related disulfide-containing analogs can be evaluated through Custom Peptide Synthesis, subject to sequence and project requirements.

Research Use Only

Apamin is supplied for research use only. It is not intended for therapeutic, or human use.