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Electrophysiological analysis of the yeast V-type proton pump: variable coupling ratio and proton shunt.

Kettner, C. ; Bertl, A. ; Obermeyer, G. ; Slayman, C. L. ; Bihler, H. (2003)
Electrophysiological analysis of the yeast V-type proton pump: variable coupling ratio and proton shunt.
In: Biophysical journal, 85 (6)
doi: 10.1016/S0006-3495(03)74789-4
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

Isolated vacuoles from the yeast Saccharomyces cerevisiae were examined in the whole-vacuole mode of patch recording, to get a detailed functional description of the vacuolar proton pump, the V-ATPase. Functioning of the V-ATPase was characterized by its current-voltage (I-V) relationship, obtained for various levels of vacuolar and cytosolic pH. I-V curves for the V-ATPase were computed as the difference between I-V curves obtained with the pump switched on (ATP, ADP, and Pi present) or off (no ATP). These difference current-voltage relationships usually crossed the voltage axis within the experimental range (from -80 to +80 mV), thus measuring the reversal voltage (ER) for the V-ATPase, which could be compared with the standing ion gradients and free energy of ATP hydrolysis, to calculate the apparent pump stoichiometry or coupling ratio: the number of protons transported for each ATP molecule hydrolyzed. This ratio was found to depend strongly upon the pH difference (DeltapH) across the vacuolar membrane, being approximately 2H+/ATP at high DeltapH (4 pH units) and increasing to >4H+/ATP for small or zero DeltapH. That result is in quantitative agreement with previous determinations on plant vacuoles. Considerations of purely electrical behavior, together with the physical properties of a recent detailed structural model for V-ATPases, led to a linear equivalent circuit--which quantitatively accounts for all observations of variable coupling ratios in fungal and plant V-ATPases by variations of the conductance for bona fide proton pumping (GP) through the ATPase relative to independent proton shunting (GS) through the same protein.

Typ des Eintrags: Artikel
Erschienen: 2003
Autor(en): Kettner, C. ; Bertl, A. ; Obermeyer, G. ; Slayman, C. L. ; Bihler, H.
Art des Eintrags: Bibliographie
Titel: Electrophysiological analysis of the yeast V-type proton pump: variable coupling ratio and proton shunt.
Sprache: Englisch
Publikationsjahr: 2003
Titel der Zeitschrift, Zeitung oder Schriftenreihe: Biophysical journal
Jahrgang/Volume einer Zeitschrift: 85
(Heft-)Nummer: 6
DOI: 10.1016/S0006-3495(03)74789-4
Kurzbeschreibung (Abstract):

Isolated vacuoles from the yeast Saccharomyces cerevisiae were examined in the whole-vacuole mode of patch recording, to get a detailed functional description of the vacuolar proton pump, the V-ATPase. Functioning of the V-ATPase was characterized by its current-voltage (I-V) relationship, obtained for various levels of vacuolar and cytosolic pH. I-V curves for the V-ATPase were computed as the difference between I-V curves obtained with the pump switched on (ATP, ADP, and Pi present) or off (no ATP). These difference current-voltage relationships usually crossed the voltage axis within the experimental range (from -80 to +80 mV), thus measuring the reversal voltage (ER) for the V-ATPase, which could be compared with the standing ion gradients and free energy of ATP hydrolysis, to calculate the apparent pump stoichiometry or coupling ratio: the number of protons transported for each ATP molecule hydrolyzed. This ratio was found to depend strongly upon the pH difference (DeltapH) across the vacuolar membrane, being approximately 2H+/ATP at high DeltapH (4 pH units) and increasing to >4H+/ATP for small or zero DeltapH. That result is in quantitative agreement with previous determinations on plant vacuoles. Considerations of purely electrical behavior, together with the physical properties of a recent detailed structural model for V-ATPases, led to a linear equivalent circuit--which quantitatively accounts for all observations of variable coupling ratios in fungal and plant V-ATPases by variations of the conductance for bona fide proton pumping (GP) through the ATPase relative to independent proton shunting (GS) through the same protein.

Fachbereich(e)/-gebiet(e): 10 Fachbereich Biologie
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10 Fachbereich Biologie > Yeast Membrane Biology
Hinterlegungsdatum: 29 Nov 2010 15:25
Letzte Änderung: 05 Mär 2013 09:41
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