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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
Internet cím:elektronikus változat
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001-es BibID:BIBFORM049067
035-os BibID:PMID:9854019
Első szerző:Szegedi Csaba
Cím:Calsequestrin : more than 'only' a luminal Ca2+ buffer inside the sarcoplasmic reticulum / Csaba Szegedi, Sarkozi Sandor, Anke Herzog, Istvan Jóna, Magdolna Varsanyi
Dátum:1999
ISSN:0264-6021
Megjegyzések:In striated muscle, the sarcoplasmic reticulum (SR) Ca2+ release/ryanodine receptor (RyR) channel provides the pathway through which stored Ca2+ is released into the myoplasm during excitation-contraction coupling. Various luminal Ca2+-binding proteins are responsible for maintaining the free [Ca2+] at 10(-3)-10(-4) M in the SR lumen; in skeletal-muscle SR, it is mainly calsequestrin. Here we show that, depending on its phosphorylation state, calsequestrin selectively controls the RyR channel activity at 1 mM free luminal [Ca2+]. Calsequestrin exclusively in the dephosphorylated state enhanced the open probability by approx. 5-fold with a Hill coefficient (h) of 3.3, and increased the mean open time by about 2-fold, i.e. solely dephosphorylated calsequestrin regulates Ca2+ release from the SR. Because calsequestrin has been found to occur mainly in the phosphorylated state in the skeletal-muscle SR for the regulation of RyR channel activity, the dephosphorylation of calsequestrin would appear to be a quintessential physiological event.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Biochemical Journal. - 337 : Pt. 1 (1999), p. 19-22. -
További szerzők:Sárközi Sándor (1966-) (élettanász) Herzog, Anke Jóna István (1948-) (élettanász, fizikus) Varsányi Magdolna
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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