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 2+ channels) in neurons. Grammotoxin is also known as omega-grammotoxin SIA.
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 2+ channels) in neurons. Grammotoxin is also known as omega-grammotoxin SIA.
Grammotoxin is a 36 Amino Acid protein toxin, which has the following sequence: Asp-Cys-Val-Arg-Phe-Trp-Gly-Lys-Cys-Ser-Gln-Thr-Ser-Asp-Cys-Cys-Pro-His-Leu-Ala-Cys-Lys-Ser-Lys-Trp-Pro-Arg-Asn-Ile-Cys-Val-Trp-Asp-Gly-Ser-Val (DCVRFWGKCSQTSDCCPHLACKSKWPRNICVWDGSV).
It forms an inhibitor cystine knot motif, common in spider toxins. [1]
Its chemical formula is: C177H268N52O50S6 [2]
Grammotoxin can be purified from Grammostola spatulata venom by reverse phase high performance liquid chromatography. [3]
The toxin binding site on the channels has high affinity for the toxins when they are closed and low affinity when channels are activated. [4] As a result, the toxin preferentially binds to the closed channels. It binds at a region which contains the voltage-sensing domains. When bound, the toxin makes it more difficult for channels to be opened by depolarization, so much larger depolarizations are required for channel activation. [4] Grammotoxin also binds to potassium channels but with lower affinity than to the calcium channels. [1]
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omega-Grammotoxin SIA (ω-grammotoxin SIA) is a protein toxin that inhibits P, Q, and N voltage-gated calcium channels (Ca2+ channels) in neurons.
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