World Library  
Flag as Inappropriate
Email this Article

Imperatoxin

Article Id: WHEBN0019683821
Reproduction Date:

Title: Imperatoxin  
Author: World Heritage Encyclopedia
Language: English
Subject:
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Imperatoxin

Imperatoxin I (IpTx) is a peptide toxin which comes 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.[1] 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.[2] The peptide acts better on RyR type 1 than on type 3. RyR type 2 seems to be insensitive to IpTxa.[3]

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.[3]

Imperatoxin I

The toxin comes from the venom of the African scorpion Pandinus imperator.[1] The structure of IpTxi consists of:

  • Two polypeptides. A large subunit of 104 amino acids and a smaller one of 27 amino acids.
  • Subunits are linked by a disulfide bond.
  • Phospholipase A2 (PLA2) activity on the large subunit.

The molecular weight of the toxin is 15 kDa.

Like IpTxa, IpTxi acts on RyR.

When an action potential reaches the muscle, RyR channels open and Ca2+ becomes available in the cell to induce contraction. The presence of Ca2+ induces the large subunit of IpTxi to hydrolyze the Sn2 fatty acyl bond from the membrane of the sarcoplasmatic reticulum. This process is executed by PLA2 activity. The freed fatty acids bind to the RyR itself or to a closely associated protein linked to gating. Binding of the RyR induces blocking of the channel. When the concentration of free fatty acids is low there will be an incomplete block of RyR; higher concentrations will give a complete block.[4]

Because IpTxi also works on the RyR channels of the heart muscles, it could potentially be used as a drug against arrhythmia. This has not yet been proven, and must be studied in vivo first.[5]

References

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.