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Imperatoxin I (IpTx) is a peptide toxin derived from the venom of the African scorpion ''Pandinus imperator''. There are two subtypes of this toxin: *Imperatoxin A (activator): a peptide toxin which enhances the influx of Ca2+ from the sarcoplasmatic reticulum into the cell. *Imperatoxin I (inhibitor): a peptide toxin which decreases the influx of Ca2+ from the sarcoplasmatic reticulum into the cell. == Imperatoxin A == The toxin comes from the venom of the African scorpion ''Pandinus imperator''. The structure of IpTxa consists of: *33 amino acids peptide. *the formula is C148H260N58O45S6. *shares the structure and function of the dihydropiridine receptor (DHPR). It corresponds to the II-III loop of the α1s subunit. *three cysteine residues that form disulfide bridges to stabilize the three-dimensional structure. The molecular weight of the toxin is 3.7 kDa. IpTxa acts on the Ryanodine receptors (RyR), which are intracellular Ca2+ release channels mainly known for their role in regulating Ca2+ release from the sarcoplasmatic reticulum of striated muscles. The peptide acts better on RyR type 1 than on type 3. RyR type 2 seems to be insensitive to IpTxa. The part of the peptide that looks like the II-III loop of the (DHPR) binds directly to RyR and enhances ryanodine binding to trigger Ca2+ release.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Imperatoxin」の詳細全文を読む スポンサード リンク
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