期刊
BIOCHEMICAL JOURNAL
卷 404, 期 -, 页码 89-96出版社
PORTLAND PRESS LTD
DOI: 10.1042/BJ20061404
关键词
dihydropyridine receptor (DHPR); hemicalcin (HCa); Hemiscorphis lepturus; homology modelling; ryanodine receptor (RyR); scorpion toxin
资金
- NIEHS NIH HHS [F32 ES005707, P30 ES005707, P42 ES004699, P42 ES04699, P42 ES05707] Funding Source: Medline
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 [H-3]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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