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001-es BibID:	BIBFORM049386
Első szerző:	Almássy János (élettanász, biológus, angol-magyar szakfordító)
Cím:	Effect of scorpion toxins on the CRC/RyR function / Janos Almassy, Balazs Lukacs, Sandor Sarkozi, Istvan Jona
Dátum:	2012
ISSN:	0006-3495
Megjegyzések:	It was shown previously that maurocalcin (MCa) induces long lasting subconductance states (LLSS) investigating the RyR function by single channel electrophysiology. These LLSSs are polarity and potential dependent and caused by the distinct positively charged surface formed by 5 amino acids corresponding to the peptide A binding site. We tested the effect of beta scorpion toxins - having a similar structure - on the RyR1 function. Charibdotoxin (CHTX) elicits close state at 20 nM in an all or none and voltage dependent manner because of smaller surface charge. Smaller size makes it easier to reach the most inner toxin binding site (out of the three) which causes the closure of the channel. MCa and CHTX share a common binding site which is identical to the peptide A binding site. Noxiustoxin has a similar effect at slightly higher toxin concentration. At nanomolar concentration Kaliotoxin evokes "flickering" of the channel in subconductance state which is occasionally interrupted by long lasting closed states, while locks the channel in closed state at micromolar concentration. Iberiotoxin induces a slight increase of the open probability accompanied by normal gating while Slotoxin has no effect. With the exception of MCa all toxins are effective only at one side, at the preferred side. Iberiotoxin and Slotoxin - ion spite of similar structure - have no large positive surfaces, they exhibit random surface charge distribution. A model has been proposed for the possible mode of action which accounts for the above effect of the tested toxins. Supported by Hungarian Research Found OTKA 81923.1563-PosB333
Tárgyszavak:	Természettudományok Biológiai tudományok idézhető absztrakt calcium release
Megjelenés:	Biophysical Journal. - 102 : 3 (2012), p. 306a-307a. -
További szerzők:	Lukács Balázs (1978-) (élettanász) Sárközi Sándor (1966-) (élettanász) Jóna István (1948-) (élettanász, fizikus)
Pályázati támogatás:	81923 OTKA
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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001-es BibID:	BIBFORM049385
Első szerző:	Csernoch László (élettanász)
Cím:	Estimation of Pore Geometry of RyR1 using Lanthanide Ruler / Laszlo Csernoch, Janos Almassy, Sandor Sarkozi, Balazs Lukacs, Istvan Jona
Dátum:	2012
ISSN:	0006-3495
Megjegyzések:	It was shown previously that the Ca analogue Gd inhibits RyR1 gating symmetrically with a Kd about 5.5 microM and Hill coefficient (nH) of 4 both on cis and trans side using single channel electrophysiology. We further tested the RyR1-lanthanide interaction using two lanthanides - having an ionic radii between Ca2+ and Gd3+ - by bilayer measurements and ryanodine binding experiments. Cis inhibition of RyR1 by Eu was characterized by a binding constant of Kd=167?5 nM and an nH of 2?0.1 while trans inhibition exhibits Kd=4.8?0.2 microM and nN of 5.2?1.2. The inhibition constants for Sm on the cis side are Kd=64.3?2.5 nM and nH=2.2?0.2 while on the trans side Kd=6.15?0.13 microM and nH=4.68?0.45. Inhibition by Eu and Sm are potential and polarity dependent in contrast to Gd due to the differences in ionic radii of these lanthanides. Increasing the ionic radius from 0.938 (Gd) to 0.964 (Sm) increased the binding affinity from 5.6 microM to 64.3 nM revealing that the size of Ca binding pocket is only slightly higher than the ionic radius of Sm. Ryanodine (Ry) binding experiments revealed that lanthanides bind - at least partially - to the regulatory Ca binding site because the dose response curve of 3H Ry binding starts with an increase of Ry binding, which amounts to about 40% for Eu and 70% for Sm of basic Ry binding. A model has been proposed for one possible spatial arrangement of lanthanide and calcium binding sites of the RyR1 pore based on the ionic radii of Ca and the tested lanthanides. Supported by OTKA 81923.1557-PosB327
Tárgyszavak:	Természettudományok Biológiai tudományok idézhető absztrakt calcium release
Megjelenés:	Biophysical Journal. - 102 : 3 Supplement (2012), p. 305a. -
További szerzők:	Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Sárközi Sándor (1966-) (élettanász) Lukács Balázs (1978-) (élettanász) Jóna István (1948-) (élettanász, fizikus)
Pályázati támogatás:	81923 OTKA
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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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)
Internet cím:	Szerző által megadott URL Intézményi repozitóriumban (DEA) tárolt változat
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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)
Internet cím:	elektronikus változat elektronikus változat DOI
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