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 ?? fb10_botanik ?? 10 Fachbereich Biologie > Yeast Membrane Biology |
| Hinterlegungsdatum: | 29 Nov 2010 15:25 |
| Letzte Änderung: | 05 Mär 2013 09:41 |
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