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. Apamin inhibits three subtypes of SK channels (K_Ca2.1, K_Ca2.2, and K_Ca2.3) with different affinity. Apamin does not affect K_Ca3.1 channel activity. Apaminmost likely acts as a pore blocker such as Scyllatoxin or Tamapin, 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.