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001-es BibID:	BIBFORM004643
Első szerző:	Berecki G.
Cím:	Anion channels in chara corallina tonoplast membrane : calcium dependence and rectification / Berecki, G., Varga, Z., Van Iren, F., Van Duijn, B.
Dátum:	1999
Megjegyzések:	Tonoplast K(+) channels of Chara corallina are well characterized but only a few reports mention anion channels, which are likely to play an important role in the tonoplast action potential and osmoregulation of this plant. For experiments internodal cells were isolated. Cytoplasmic droplets were formed in an iso-osmotic bath solution according to a modified procedure. Ion channels with conductances of 48 pS and 170 pS were detected by the patch-clamp technique. In the absence of K(+) in the bath solution the 170 pS channel was not observed at negative pipette potential values. When Cl(-) on either the vacuolar side or the cytoplasmic side was partly replaced with F(-), the reversal potential of the 48 pS channel shifted conform to the Cl(-) equilibrium potential with similar behavior in droplet-attached and excised patch mode. These results showed that the 48 pS channel was a Cl(-) channel. In droplet-attached mode the channel rectified outward current flow, and the slope conductance was smaller. When Chara droplets were formed in a bath solution containing low (10(-8) m) Ca(2+), then no Cl(-) channels could be detected either in droplet-attached or in inside-out patch mode. Channel activity was restored if Ca(2+) was applied to the cytoplasmic side of inside-out patches. Rectification properties in the inside-out patch configuration could be controlled by the holding pipette potential. Holding potential values negative or positive to the calculated reversal potential for Cl(-) ions induced opposite rectification properties. Our results show Ca(2+)-activated Cl(-) channels in the tonoplast of Chara with holding potential dependent rectification
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban Action Potentials agonists Algae, Green Animal Anions antagonists and inhibitors Calcium Cesium Chloride Channels Chlorides cytology Cytoplasm drug effects Electric Conductivity Fluorine Ion Channel Gating metabolism Osmolar Concentration Patch-Clamp Techniques pharmacology Plant Proteins Potassium Potassium Channels Sodium Substrate Specificity Support, Non-U.S.Gov't Vacuoles Zinc
Megjelenés:	The Journal of Membrane Biology. - 172 : 2 (1999), p. 159-168. -
További szerzők:	Varga Zoltán (1969-) (biofizikus, szakfordító) Iren, F., Van Duijn, B., Van
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001-es BibID:	BIBFORM004689
Első szerző:	Péter Mózes (orvos, neuroradiológus) ifj.
Cím:	Effects of toxins Pi2 and Pi3 on human T lymphocyte Kv1.3 channels : the role of Glu7 and Lys24 / Peter, M., Jr., Varga, Z., Hajdu, P., Gaspar, R., Damjanovich, S., Horjales, E., Possani, L. D., Panyi, G.
Dátum:	2001
Megjegyzések:	Pandinus imperator scorpion toxins Pi2 and Pi3 differ only by a single amino acid residue (neutral Pro7 in Pi2 vs. acidic Glu7 in Pi3). The binding kinetics of these toxins to human Kv1.3 showed that the decreased ON rate (k(ON) = 2.18 x 10(8) m(-1)sec(-1) for Pi2 and 1.28 x 10(7) m(-1)sec(-1) for Pi3) was almost entirely responsible for the increased dissociation constant (K(d)) of Pi3 (K(d) = 795 pm) as compared to Pi2 (K(d) = 44 pm). The ionic strength dependence of the association rates was exactly the same for the two toxins indicating that through-space electrostatic interactions can not account for the different ON rates. Results were further analyzed on the basis of the three-dimensional structural models of the toxins. A 3D structure of Pi3 was generated from the NMR spectroscopy coordinates of Pi2 by computer modeling. The Pi3 model resulted in a salt bridge between Glu7 and Lys24 in Pi3. Based on this finding our interpretation of the reduced ON rate of Pi3 is that the intramolecular salt bridge reduces the local positive electrostatic potential around Lys24 resulting in decreased short-range electrostatic interactions during the binding step. To support our finding, we constructed a 3D model of the Ser-10-Asp Charybdotoxin mutant displaying distinctly reduced affinity for Shaker channels. The mutant Charybdotoxin structure also displayed a salt bridge between residues Asp10 and Lys27 equivalent to the one between Glu7 and Lys24 in Pi3.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban Amino Acid Sequence Animal Charybdotoxin chemistry drug effects genetics Glutamic Acid Human Hungary In Vitro Kinetics Lysine Membrane Potentials metabolism Models,Molecular Molecular Sequence Data pharmacology Point Mutation Potassium Potassium Channel Blockers Potassium Channels Protein Conformation Scorpion Venoms Sequence Homology,Amino Acid Support,Non-U.S.Gov't T-Lymphocytes Toxins
Megjelenés:	The Journal of Membrane Biology. - 179 : 1 (2001), p. 13-25. -
További szerzők:	Varga Zoltán (1969-) (biofizikus, szakfordító) Hajdu Péter (1975-) (biofizikus) Gáspár Rezső (1944-) (biofizikus) Damjanovich Sándor (1936-2017) (biofizikus) Horjales, E. Possani, Lourival Domingos Panyi György (1966-) (biofizikus)
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