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001-es BibID:BIBFORM049379
Első szerző:Lukács Balázs (élettanász)
Cím:Effect of maurocalcine on the skeletal type ryanodine receptor / Lukacs B., Sarkozi S., Almassy J., Jona I.
Megjegyzések:Maurocalcine (MCa) is a 33 amino acid long scorpion toxin which shows high homology with dihydropyridine receptor constituent peptide-A (pepA). The latter is believed to directly interact with ryanodine receptor (RyR1) and plays important role in the electromechanical coupling. The position and the positive charge of given amino acids residues of MCa are determinative in this interaction.We studied the effect of pepA and potassium ion on the MCa evoked Long Lasting Subconductance State (LLSS) type RyR1 operation assuming that both of them may have access to MCa binding sites of the channel. To investigate the binding of these peptides to RyR1, we used heavy sarcoplasmic reticulum vesicles (HSR) and CHAPS solubilized ryanodine receptor complex of rabbit skeletal muscle. Gating of RyR1 was monitored on channels incorporated into a planar lipid bilayer under voltage clamp conditions. Ca2+-release measurements were performed on HSR, where changes in extravesicular Ca2+ concentration were followed as changes in the absorption of APIII Ca2+-sensitive dye (?=710 nm).In single channel experiments LLSS type RyR1 gating was evoked applying of 5 and 10 nM MCa in the cytoplasmic side of the channel. The length and frequency of the characteristic subconductance states gradually ceased by consecutively added K+. The half effective concentration of K+ was higher at 10 nM MCa concentration which refers to a possible competition between MCa and potassium ion in biding to the same site on RyR1. A similar competitive-like effect of pepA was observed, when in the presence of 26 ?M pepA, much higher concentration of MCa was able to evoke LLSSs. In Ca2+ release measurements 5 nM MCa induced Ca2+-release at 100 mM K+, but release was completely eliminated at 250 mM K+. High concentration of K+inhibited only the MCa induced Ca2+-release but had no effect on the 4-CMC induced Ca2+-release suggesting specific effect of K+ on MCa-RyR1 interaction. Suppression of release in the presence of 250 mM K+ was inhibited by addition of higher concentration of MCa suggesting charge driven interaction between MCa and RyR1.Our data put forward a possible mode of MCa action with 3 binding sites at the cytosolic side on RyR1. The first binding site located on the surface of the channel, and is responsible for the Po increase at low MCa concentration. The second binding site in the pore of the channel induces potential- and voltage dependent LLSS-s at higher toxin concentration. Occupy of third one which located presumably in the pore, close to the selectivity filter results in closed states of RyR1.Supported by: OTKA 81923
Tárgyszavak:Természettudományok Biológiai tudományok idézhető absztrakt
calcium release
Megjelenés:Acta Physiologica. - 205 : Suppl. 690 (2012), 26. p. -
További szerzők:Sárközi Sándor (1966-) (élettanász) Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Jóna István (1948-) (élettanász, fizikus)
Pályázati támogatás:81923
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