Eintrag weiter verarbeiten
Verfügbar über Online-Ressource

Comparison of the H + /ATP ratios of the H + -ATP synthases from yeast and from chloroplast

Gespeichert in:

Bibliographische Detailangaben
Zeitschriftentitel: Proceedings of the National Academy of Sciences
Personen und Körperschaften: Petersen, Jan, Förster, Kathrin, Turina, Paola, Gräber, Peter
In: Proceedings of the National Academy of Sciences, 109, 2012, 28, S. 11150-11155
Format: E-Article
Sprache: Englisch
veröffentlicht:
Proceedings of the National Academy of Sciences
Schlagwörter:
Multidisciplinary
Details
Zusammenfassung: <jats:p> F <jats:sub>0</jats:sub> F <jats:sub>1</jats:sub> -ATP synthases use the free energy derived from a transmembrane proton transport to synthesize ATP from ADP and inorganic phosphate. The number of protons translocated per ATP (H <jats:sup>+</jats:sup> /ATP ratio) is an important parameter for the mechanism of the enzyme and for energy transduction in cells. Current models of rotational catalysis predict that the H <jats:sup>+</jats:sup> /ATP ratio is identical to the stoichiometric ratio of c-subunits to β-subunits. We measured in parallel the H <jats:sup>+</jats:sup> /ATP ratios at equilibrium of purified F <jats:sub>0</jats:sub> F <jats:sub>1</jats:sub> s from yeast mitochondria (c/β = 3.3) and from spinach chloroplasts (c/β = 4.7). The isolated enzymes were reconstituted into liposomes and, after energization of the proteoliposomes with acid–base transitions, the initial rates of ATP synthesis and hydrolysis were measured as a function of ΔpH. The equilibrium ΔpH was obtained by interpolation, and from its dependency on the stoichiometric ratio, [ATP]/([ADP]·[P <jats:sub>i</jats:sub> ]), finally the thermodynamic H <jats:sup>+</jats:sup> /ATP ratios were obtained: 2.9 ± 0.2 for the mitochondrial enzyme and 3.9 ± 0.3 for the chloroplast enzyme. The data show that the thermodynamic H <jats:sup>+</jats:sup> /ATP ratio depends on the stoichiometry of the c-subunit, although it is not identical to the c/β ratio. </jats:p>
Umfang: 11150-11155
ISSN: 0027-8424
1091-6490
DOI: 10.1073/pnas.1202799109