Апамин

Химические свойства

Small, highly potent, highly basic polypeptide.

Использование

Apamin has been used:

• As a selective inhibitor of small conductance (SKCa) channels in HEK cells.
• To inhibit endothelium-derived relaxing factor (EDHF) mediated responses.
• To block small-conductance Ca₂-activated K current (ISK) in electrophysiological studies in hyperstriatum ventrale, pars caudalis (HVc) neurons.

Определение

Occurs in the venom of the honey bee, Apis mellifera; molecular weight of 2027.38.

Общее описание

Apamin is a bee venom component and is strongly basic in nature. It has 18 amino acid residues and two disulphide bonds.

Опасность

Central nervous system poison able to cross the blood–brain barrier; neurotoxic; poison.

Профиль безопасности

Poison by intravenous, parenteral,intracerebral, and intraperitoneal routes. When heated todecomposition it emits toxic fumes of SOx and NOx.

Ферментативный ингибитор

This bee venom octadecapeptide toxin (FW = 2027.34 g/mol; CAS 24345- 16-2; NCBI Reference Sequence: NP_001011612.1) potently blocks the small-conductance Ca 2+ -activated potassium ion (or SK) channels hSK1 as well as rSK2, with IC50 values of 3.3 nM and 83 pM. It shows greater effectiveness at the SK2 channel (IC50 = 0.06-0.4 nM) than SK1 (IC50 = 1- 12 nM). SK3 (IC50 = 1-13 nM), and SK4 (IC50 = 1 μM) channels, and is active against channels within neurons, vascular endothelium, bladder smooth muscle, and certain cancers. Apamin does not inhibit human cardiac Na + current, L-type Ca 2+ current or other major K+ currents. Structurally, apamin forms a stable structure, consisting of a C-terminal a- helix and two reverse turns, that is stabilized by two disulfide bonds connecting Cys-1 to Cys-11 and Cys-3 to Cys-15. A minor constituent of venom of the bee (Apis mellifera), apamin amounts to only 2-3% (w/w) of its dry venom. The smallest known neurotoxic polypeptide, apamin is derived by proteolytic processing of the 48-residue pre-pro-protein. The precursors of the bee venom constituents apamin and MCD peptide are encoded by two genes in tandem which share the same 3'-exon.