Chemical synthesis and characterization of maurocalcine, a scorpion toxin that activates Ca²⁺ release channel/ryanodine receptors

Abstract

Maurocalcine is a novel toxin isolated from the venom of the chactid scorpion Scorpio maurus palmatus. It is a 33-mer basic peptide cross-linked by three disulfide bridges, which shares 82% sequence identity with imperatoxin A, a scorpion toxin from the venom of Pandinus imperator. Maurocalcine is peculiar in terms of structural properties since it does not possess any consensus motif reported so far in other scorpion toxins. Due to its low concentration in venom (0.5% of the proteins), maurocalcine was chemically synthesized by means of an optimized solid-phase method, and purified after folding/oxidation by using both C18 reversed-phase and ion exchange highpressure liquid chromatographies. The synthetic product (sMCa) was characterized. The half-cystine pairing pattern of sMCa was identified by enzyme-based cleavage and Edman sequencing. The pairings were Cys3-Cys17, Cys10-Cys21, and Cys16-Cys32. In vivo, the sMCa was lethal to mice following intracerebroventricular inoculation (LD 50 , 20 W Wg/mouse). In vitro, electrophysiological experiments based on recordings of single channels incorporated into planar lipid bilayers showed that sMCa potently and reversibly modifies channel gating behavior of the type 1 ryanodine receptor by inducing prominent subconductance behavior.z 2000 Federation of European Biochemical Societies.

One scorpion, two venoms: Prevenom ofParabuthus transvaalicusacts as an alternative type of venom with distinct mechanism of action

“…In the venom mixture, there are peptides that are specialized against vertebrates, invertebrates, or active against both. Members of all three groups are well characterized and include peptides that target all of the major ion channel types such as Na ϩ , K ϩ , Cl Ϫ , Ca 2ϩ , and ryanodine-sensitive Ca 2ϩ channels (9)(10)(11)(12). The devastating potency of the venom is caused by its ability to target multiple types of ion channels simultaneously, resulting in a massive and recurring depolarization that disables or kills the prey or predator.…”

Maurocalcine and Peptide A Stabilize Distinct Subconductance States of Ryanodine Receptor Type 1, Revealing a Proportional Gating Mechanism

“…Recently, maurocalcine (MCa), a novel peptide isolated from the venom of the scorpion Scorpio maurus palmatus, has been found to possess 82% sequence identity with IpTx a (27,28). MCa shares the highly basic structural domain identified in peptide A and IpTx a important for interactions with RyR1.…”

“…MCa shares the highly basic structural domain identified in peptide A and IpTx a important for interactions with RyR1. Preliminary work has shown that synthetic MCa (sMCa) activates RyR1 channels by inducing long living subconductance states (27). Both IpTx a -and sMCa-modified channels can reversibly transit between subconductance states and fast gating states.…”

“…However, the predominant subconductance induced by sMCa differs from that of IpTx a . At a holding potential of ϩ40 mV, the predominant substates induced by sMCa and IpTx a are 48 and 28% of the full conductance, respectively, suggesting that the structural difference in these peptides may induce slightly different channel conformations that stabilize different unitary conductances (25,27).…”

Administration de molécules actives dans les cellules

“…Ce peptide de 33 acides aminés fut identifié grâce à son activité pharmacologique en tant qu'activateur du récepteur à la ryanodine (RyR1) des muscles squelettiques. La cible est particulièrement originale puisqu'il s'agit d'un canal calcique intracellulaire impliqué dans le couplage excitation-contraction [6]. Ces observations avaient laissé entrevoir la possibilité que la maurocalcine devait traverser la bicouche lipidique des cellules afin d'exercer sa fonction d'activateur de canal calcique.…”