Maurocalcine and peptide A stabilize distinct subconductance states of ryanodine receptor type 1, revealing a proportional gating mechanism

Lili Chen, Eric Estève, Jean Marc Sabatier, Michel Ronjat, Michel De Waard, Paul D. Allen, Isaac N Pessah

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34 Scopus citations


Maurocalcine (MCa) isolated from Scorpio maurus palmatus venom shares 82% sequence identity with imperatoxin A. Both scorpion toxins are putative mimics of the II-III loop peptide (termed peptide A (pA)) of α1s-dihydropyridine receptor and are thought to act at a common site on ryanodine receptor type 1 (RyR1) important for skeletal muscle EC coupling. The relationship between the actions of synthetic MCa (sMCa) and pA on RyR1 were examined. sMCa released Ca2+ from SR vesicles (EC50 = 17.5 nM) in a manner inhibited by micromolar ryanodine or ruthenium red. pA (0.5-40 μM) failed to induce SR Ca2+ release. Rather, pA enhanced Ca2+ loading into SR and fully inhibited Ca2+-, caffeine-, and sMCa-induced Ca2+ release. The two peptides modified single channel gating behavior in distinct ways. With Cs+-carrying current, 10 nM to 1 μM sMCa induced long lived subconductances having 48% of the characteristic full open state and occasional transitions to 29% at either positive or negative holding potentials. In contrast, pA stabilized long lived channel closures with occasional burst transitions to 65% (sl) and 86% (s2) of the full conductance. The actions of pA and sMCa were observed in tandem. sMCa stabilized additional subconductance states proportional to pA-induced subconductances (i.e. 43% of pA-modified s1 and s2 substates), revealing a proportional gating mechanism. [3H]Ryanodine binding and surface plasmon resonance analyses indicated that the peptides did not interact by simple competition for a single class of mutually exclusive sites on RyR1 to produce proportional gating. The actions of sMCa were also observed with ryanodine-modified channels and channels deficient in immunophilin 12-kDa FK506-binding protein. These results provide evidence that sMCa and pA stabilize distinct RyR1 channel states through distinct mechanisms that allosterically stabilize gating states having proportional conductance.

Original languageEnglish (US)
Pages (from-to)16095-16106
Number of pages12
JournalJournal of Biological Chemistry
Issue number18
StatePublished - May 2 2003

ASJC Scopus subject areas

  • Biochemistry


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