Open AccessATP‐regulation of cytochrome oxidase in yeast mitochondria
Author(s) -
Beauvoit Bertrand,
Bunoust Odile,
Guérin Bernard,
Rigoulet Michel
Publication year - 1999
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.1999.00475.x
Subject(s) - cytochrome c oxidase , biochemistry , oxidase test , protein subunit , mitochondrion , electron transport chain , cytochrome , cytochrome c , chemiosmosis , respiratory chain , electron transport complex iv , biology , cytochrome c1 , atp synthase , cytosol , biophysics , coenzyme q – cytochrome c reductase , enzyme , gene
The role of the nuclear‐encoded subunit VIa in the regulation of cytochrome oxidase by ATP was investigated in isolated yeast mitochondria. As the subunit VIa‐null strain possesses a fully active and assembled cytochrome oxidase, multiple ATP‐regulating sites were characterized with respect to their location and their kinetic effect: (a) intra‐mitochondrial ATP inhibited the complex IV activity of the null strain, whereas the prevailing effect of ATP on the wild‐type strain, at low ionic strength, was activation on the cytosolic side of complex IV, mediated by subunit VIa. However, at physiological ionic strength (i.e. ≈ 200 m m ), activation by ATP was absent but inhibition was not impaired; (b) in ethanol‐respiring mitochondria, when the electron flux was modulated using a protonophoric uncoupler, the redox state of aa 3 cytochromes varied with respect to activation (wild‐type) or inhibition (null‐mutant) of the cytochrome oxidase by ATP; (c) consequently, the control coefficient of cytochrome oxidase on respiratory flux, decreased (wild‐type) or increased (null‐mutant) in the presence of ATP; (d) considering electron transport from cytochrome c to oxygen, the response of cytochrome oxidase to its thermodynamic driving force was increased by ATP for the wild‐type but not for the mutant subunit. Taken together, these findings indicate that at physiological concentration, ATP regulates yeast cytochrome oxidase via subunit‐mediated interactions on both sides of the inner membrane, thus subtly tuning the thermodynamic and kinetic control of respiration. This study opens up new prospects for understanding the feedback regulation of the respiratory chain by ATP.