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001-es BibID:	BIBFORM001016
Első szerző:	Altafaj, Xavier
Cím:	Maurocalcine interacts with the cardiac ryanodine receptor without inducing channel modification / Altafaj X., France J., Almássy J., Jóna I., Rossi D., Sorrentino V., Mabrouk K., De Waard M., Ronjat M.
Dátum:	2007
Megjegyzések:	We have previously shown that MCa (maurocalcine), a toxin from the venom of the scorpion Maurus palmatus, binds to RyR1 (type 1 ryanodine receptor) and induces strong modifications of its gating behaviour. In the present study, we investigated the ability of MCa to bind to and modify the gating process of cardiac RyR2. By performing pull-down experiments we show that MCa interacts directly with RyR2with an apparent affinity of 150 nM. By expressing different domains of RyR2 in vitro, we show that MCa binds to two domains of RyR2, which are homologous with those previously identified on RyR1. The effect of MCa binding to RyR2 was then evaluated by three different approaches: (i) [H-3]ryanodine binding experiments, showing a very weak effect of MCa (up to 1 mu M), (ii) Ca2+ release measurements from cardiac sarcoplasmic reticulum vesicles, showing that MCa up to 1 mu M is unable to induce Ca2+ release, and (iii) single-channel recordings, showing that MCa has no effect on the open probability or on the RyR2 channel conductance level. Long-lasting opening events of RyR2 were observed in the presence of MCa only when the ionic current direction was opposite to the physiological direction, i.e. from the cytoplasmic face of RyR2 to its luminal face. Therefore, despite the conserved MCa binding ability of RyR1 and RyR2, functional studies show that, in contrast with what is observed with RyR1, MCa does not affect the gating properties of RyR2. These results highlight a different role of the MCa-binding domains in the gating process of RyR1 and RyR2.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Biochemical Journal 406 (2007), p. 309-315. -
További szerzők:	France, Julien Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Jóna István (1948-) (élettanász, fizikus) Rossi, Daniela Sorrentino, Vincenzo Mabrouk, Kamel De Waard, Michel Ronjat, Michel
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001-es BibID:	BIBFORM049390
Első szerző:	Jóna István (élettanász, fizikus)
Cím:	Effect of maurocalcine on RyR1 and RyR2 is substantially different / Istvan Jona, Janos Almassy, Michel Ronjat, Balazs Lukacs
Dátum:	2007
ISSN:	0006-3495
Megjegyzések:	Effect of a scorpion toxin (maurocalcine, MCa) on the RyR was studied using Müller-Rudin type bilayer. Canine cardiac SR calcium channel (RyR2) was isolated, solubilized and incorporated into lipid bilayer. Channel parameters were determined under voltage clamp conditions, using charge carrier of 250 mM KCl while ionized calcium buffered to 274 nM and 50 microM. It is shown that MCa evokes long lasting subconductance state (LLSS) events if the current is opposite of the physiological calcium movement - similarly to RyR1 (as prviously reported), but these events in case of RyR2 are more frequent [63.5 ? 5.7 versus 17.3 ? 2.7 in a minute] and about 10 times shorter [12 ? 0.9 sec versus 193 ? 14 ms] than in case of RyR1. During these LLSS events, the channel frequently goes into the close state - for a short period - end returns to the subconductance state. These intra-LLSS closings are longer for the RyR2-MCa interaction than for the RyR1-MCa interaction. The open probability (Po) - determined between the LLSS events - is also effected. In case of physiological current MCa does not evoke LLSS at all, however there is a slight increase of the open probability. Similarly to the RyR1, the effect of the toxin on RyR2 is voltage independent and its concentration dependence indicates one binding site. The MCa effect is calcium independent. These findings indicate that the region of the RyR2 which interacts with the 2-3 loop of the DHPR is different from that of the RyR1.
Tárgyszavak:	Természettudományok Biológiai tudományok idézhető absztrakt calcium release
Megjelenés:	Biophysical Journal. - 91 : Suppl. (2007), p. 87a. -
További szerzők:	Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Ronjat, Michel Lukács Balázs (1978-) (élettanász)
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001-es BibID:	BIBFORM004115
Első szerző:	Lukács Balázs (élettanász)
Cím:	Charged surface area of maurocalcine determines its interaction with the skeletal ryanodine receptor / Balazs Lukacs, Monika Sztretye, Janos Almassy, Sandor Sarkozi, Beatrix Dienes, Kamel Mabrouk, Cecilia Simut, Laszlo Szabo, Peter Szentesi, Michel De Waard, Michel Ronjat, Istvan Jona, Laszlo Csernoch
Dátum:	2008
Megjegyzések:	The 33 amino acid scorpion toxin maurocalcine (MCa) has been shown to modify the gating of the skeletal-type ryanodine receptor (RyR1). Here we explored the effects of MCa and its mutants ([Ala(8)]MCa, [Ala(19)]MCa, [Ala(20)]MCa, [Ala(22)]MCa, [Ala(23)]MCa, and [Ala(24)]MCa) on RyR1 incorporated into artificial lipid bilayers and on elementary calcium release events (ECRE) in rat and frog skeletal muscle fibers. The peptides induced long-lasting subconductance states (LLSS) on RyR1 that lasted for several seconds. However, their average length and frequency were decreased if the mutation was placed farther away in the 3D structure from the critical (24)Arg residue. The effect was strongly dependent on the direction of the current through the channel. If the direction was similar to that followed by calcium during release, the peptides were 8- to 10-fold less effective. In fibers long-lasting calcium release events were observed after the addition of the peptides. The average length of these events correlated well with the duration of LLSS. These data suggest that the effect of the peptide is governed by the large charged surface formed by residues Lys(20), Lys(22), Arg(23), Arg(24), and Lys(8). Our observations also indicate that the results from bilayer experiments mimic the in situ effects of MCa on RyR1.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Biophysical Journal. - 95 : 7 (2008), p. 3497-3509. -
További szerzők:	Sztretye Mónika (1981-) (élettanász, elektrofiziológus) Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Sárközi Sándor (1966-) (élettanász) Dienes Beatrix (1972-) (élettanász, molekuláris biológus) Mabrouk, Kamel Simut, Cecilia Szabó László (Románia) Szentesi Péter (1967-) (élettanász) De Waard, Michel Ronjat, Michel Jóna István (1948-) (élettanász, fizikus) Csernoch László (1961-) (élettanász)
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001-es BibID:	BIBFORM049411
Első szerző:	Szentesi Péter (élettanász)
Cím:	Mutations in the scorpion toxin maurocalcine alter its ability to modify the calcium release events in frog skeletal muscle / P. Szentesi, J. Almássy, M. Fehér, B. Dienes, C. A. Simut, I. Jona, M. Ronjat, L. Csernoch
Dátum:	2006
Megjegyzések:	Maurocalcine (MCa), a 33 amino acid toxin obtained from the venom of Scorpio Maurus Palmatus, has been shown to interact with the isolated skeletal-type ryanodine receptor (RyR1) and to strongly modify its calcium channel gating. In this study, we explored the effects of MCa and its mutants (Lys8Ala, Lys19Ala and Lys22Ala) on elementary calcium release events in frog skeletal muscle fibers.Fibers were mechanically dissected, chemically skinned with saponin and imaged by a laser scanning confocal microscope in line scan mode in the presence of MCa and its mutants.Long lasting spontaneous calcium release events (embers), were observed after the addition of the toxins which were never seen under control conditions. Two typical forms of embers: with or without a classical spark were identified. The length of the embers correlated well with the duration of the long lasting sub-conductance states seen on MCa-modified RyR1-s incorporated into planar lipid bilayers. In particular, the Lys8Ala and Lys19Ala mutants had similar effects as the wild type MCa and produced long (430.9 ? 42.9, 442.6 ? 19.4 ms), while the Lys22Ala mutant induced shorter (65.3 ? 7.5 ms) events. Our observations indicate that the results from artificial lipid bilayer experiments mimic the in situ effects of MCa on RyR. We propose that an ember reflects the calcium release from a single release unit modified by the toxin.
Tárgyszavak:	Természettudományok Biológiai tudományok idézhető absztrakt calcium release
Megjelenés:	Journal of Muscle Research and Cell Motility. - 27 (2006), p. 516. -
További szerzők:	Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Fehér Miklós Dienes Beatrix (1972-) (élettanász, molekuláris biológus) Simut, Cecilia Jóna István (1948-) (élettanász, fizikus) Ronjat, Michel Csernoch László (1961-) (élettanász)
Internet cím:	Szerző által megadott URL Intézményi repozitóriumban (DEA) tárolt változat
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