Grammotoxin
![Solution structure of omega-grammotoxin SIA. PDB entry 1koz[1]](/Images/godic/202501/16/1koz5537.jpg")
Grammotoxin is a toxin in the venom of the tarantula Grammostola spatulata. It is a protein toxin that inhibits P-, Q- and N-type voltage-gated calcium channels (Ca channels) in neurons. Grammotoxin is also known as omega-grammotoxin SIA.