Hemicalcin, a new toxin from the Iranian scorpion Hemiscorpius lepturus which is active on ryanodine-sensitive Ca2+ channels.

نویسندگان

  • Delavar Shahbazzadeh
  • Najet Srairi-Abid
  • Wei Feng
  • Narendra Ram
  • Lamia Borchani
  • Michel Ronjat
  • Abolfazl Akbari
  • Isaac N Pessah
  • Michel De Waard
  • Mohamed El Ayeb
چکیده

In the present work, we purified and characterized a novel toxin named hemicalcin from the venom of the Iranian chactoid scorpion Hemiscorpius lepturus where it represents 0.6% of the total protein content. It is a 33-mer basic peptide reticulated by three disulfide bridges, and that shares between 85 and 91% sequence identity with four other toxins, all known or supposed to be active on ryanodine-sensitive calcium channels. Hemicalcin differs from these other toxins by seven amino acids at positions 9 (leucine/arginine), 12 (alanine/glutamic acid), 13 (aspartic acid/asparagine), 14 (lysine/asparagine), 18 (serine/glycine), 26 (threonine/alanine) and 28 (proline/isoleucine/alanine). In spite of these differences, hemicalcin remains active on ryanodine-sensitive Ca2+ channels, since it increases [3H]ryanodine binding on RyR1 (ryanodine receptor type 1) and triggers Ca2+ release from sarcoplasmic vesicles. Bilayer lipid membrane experiments, in which the RyR1 channel is reconstituted and its gating properties are analysed, indicate that hemicalcin promotes an increase in the opening probability at intermediate concentration and induces a long-lasting subconductance level of 38% of the original amplitude at higher concentrations. Mice intracerebroventricular inoculation of 300 ng of hemicalcin induces neurotoxic symptoms in vivo, followed by death. Overall, these data identify a new biologically active toxin that belongs to a family of peptides active on the ryanodine-sensitive channel.

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منابع مشابه

A review of epidemiological, clinical and in vitro physiological studies of envenomation by the scorpion Hemiscorpius lepturus (Hemiscorpiidae) in Iran.

Many of the published accounts of envenomation by Hemiscorpius lepturus (H. lepturus) are in a form that makes it difficult for non Farsi readers to access. The purpose of this review is to summarise the Iranian literature on the toxinological effects of the venom of H. lepturus using both in vivo and in vitro data and where appropriate, details of methods and ethics statements will be reported.

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عنوان ژورنال:
  • The Biochemical journal

دوره 404 1  شماره 

صفحات  -

تاریخ انتشار 2007