title: Maurocalcine and domain A of the II-III loop of the dihydropyridine receptor Cav 1.1 subunit share common binding sites on the skeletal ryanodine receptor.
abstract: Maurocalcine is a scorpion venom toxin of 33 residues that bears a striking resemblance to the domain A of the dihydropyridine voltage-dependent calcium channel type 1.1 (Cav1.1) subunit. This domain belongs to the II-III loop of Cav1.1, which is implicated in excitation-contraction coupling. Besides the structural homology, maurocalcine also modulates RyR1 channel activity in a manner akin to a synthetic peptide of domain A. Because of these similarities, we hypothesized that maurocalcine and domain A may bind onto an identical region(s) of RyR1. Using a set of RyR1 fragments, we demonstrate that peptide A and maurocalcine bind onto two discrete RyR1 regions: fragments 3 and 7 encompassing residues 1021-1631 and 3201-3661, respectively. The binding onto fragment 7 is of greater importance and was thus further investigated. We found that the amino acid region 3351-3507 of RyR1 (fragment 7.2) is sufficient for these interactions. Proof that peptide A and maurocalcine bind onto the same site is provided by competition experiments in which binding of fragment 7.2 to peptide A is inhibited by preincubation with maurocalcine. Moreover, when expressed in COS-7 cells, RyR1 carrying a deletion of fragment 7 shows a loss of interaction with both peptide A and maurocalcine. At the functional level, this deletion abolishes the maurocalcine induced stimulation of [3H]ryanodine binding onto microsomes of transfected COS-7 cells without affecting the caffeine and ATP responses.
authors.affiliation: INSERM U607/DRDC, CEA, 17 rue des Martyrs, 38054 Grenoble Cedex 09, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: Altafaj
authors.forename: Weijun
authors.initials: W
authors.lastname: Cheng
authors.forename: Eric
authors.initials: E
authors.lastname: Estève
authors.forename: Julie
authors.initials: J
authors.lastname: Urbani
authors.forename: Didier
authors.initials: D
authors.lastname: Grunwald
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Sabatier
authors.forename: Roberto
authors.initials: R
authors.lastname: Coronado
authors.forename: Michel
authors.initials: M
authors.lastname: De Waard
authors.forename: Michel
authors.initials: M
authors.lastname: Ronjat
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D019556:COS Cells; D020746:Calcium Channels, L-Type / Q000737:chemistry*; D051242:Caveolin 1; D022461:Caveolins / Q000737:chemistry*; D002845:Chromatography; D003001:Cloning, Molecular; D020285:Cryoelectron Microscopy; D008856:Microscopy, Fluorescence; D018482:Muscle, Skeletal / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012433:Ryanodine / Q000737:chemistry; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry; D012604:Scorpion Venoms / Q000737:chemistry / Q000494:pharmacology*; D014162:Transfection
chemical_list: D020746:Calcium Channels, L-Type; D051242:Caveolin 1; D022461:Caveolins; D010455:Peptides; D011993:Recombinant Fusion Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D012604:Scorpion Venoms; C406406:maurocalcine; D012433:Ryanodine; D000255:Adenosine Triphosphate