Other · Disulphide-rich potassium-channel-blocking peptide
Apamin
Also known as —
An 18-residue honeybee venom peptide used to identify apamin-sensitive KCa2 potassium currents in electrophysiological research.
- Length
- 18 amino acids
- Half-life
- Not well characterised
- Mechanism
- Apamin blocks apamin-sensitive small-conductance calcium-activated potassium channels of the KCa2 family by binding at their extracellular surface. Sensitivity differs between KCa2.1, KCa2.2 and KCa2.3 channels and depends on species and channel composition.
- Studied in
- Patch-clamp experiments, neuronal cultures and animal brain-slice models use apamin to investigate KCa2-dependent afterhyperpolarisation, firing patterns and synaptic plasticity.
About Apamin
Apamin is a compact peptide originally isolated from the venom of the honeybee, Apis mellifera, and characterised during the 1960s. Its 18-residue chain contains two disulphide bonds, with connectivity between cysteines 1–11 and 3–15, and an amidated C-terminus. These features constrain a small, basic structure whose exposed residues support channel recognition. The native molecular form is therefore defined by both its amino-acid sequence and its post-translational chemistry, rather than chain length alone.
The principal laboratory targets are small-conductance calcium-activated potassium channels, designated KCa2.1, KCa2.2 and KCa2.3. KCa2.2 is generally especially sensitive, whereas KCa2.1 sensitivity varies markedly between species and experimental constructs. These channels couple intracellular calcium signals to potassium conductance through associated calmodulin. By inhibiting their extracellularly accessible channel machinery, apamin helps resolve their contribution to neuronal afterhyperpolarisation and excitability. An apamin-sensitive current should not automatically be assigned to one KCa2 subtype without additional controls.
Laboratory notes
- Confirm the native disulphide connectivity and C-terminal amidation; intact mass alone does not establish correct folding.
- Use low-binding labware and validate recovery at low assay concentrations, where adsorption can distort apparent potency.
- For research use only. Handle as a potent neuroactive toxin under an institutional risk assessment and consult the product-specific safety data sheet.
Storage and reconstitution basics: storage guide.
Questions about Apamin
Does apamin distinguish individual KCa2 subtypes?
Not reliably by itself. Subtypes differ in sensitivity, but species, heteromeric assembly and assay conditions complicate subtype assignment.
Does apamin block all calcium-activated potassium channels?
No. It is principally a probe for apamin-sensitive KCa2 channels, not a general blocker of KCa3.1 or large-conductance KCa1.1 channels.
Why does C-terminal amidation matter for a reference material?
Amidation is part of native apamin's chemical identity and changes terminal charge. An unamidated preparation should not be assumed equivalent without comparative characterisation.
Is Apamin for human use?
No. It is supplied strictly for in-vitro laboratory research and is not for human or animal consumption.
Related research peptides
All products are sold for laboratory research use only. Not for human consumption, not a medicine, not for diagnosing, treating or preventing any condition.