Apamin

Apamin is a neurotoxin that was originally isolated from Apis mellifera. Apamin binds to and inhibits the SK channels (small conductance Ca2+-activated K+ channels) in the brain and spinal cord. It inhibits three subtypes of SK channels (SK1, SK2, and SK3) with different affinity. Apamin most likely acts as a pore blocker, although residues both inside and outside of the pore region of the SK channels participate in apamin binding. The SK channels are present in a wide range of excitable and non-excitable cells, including cells in the central nervous system, intestinal myocytes, endothelial cells, and hepatocytes.