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Respiration of mitochondria in living organisms is controlled by the ATP/ADP ratio and phosphorylation pattern of cytochrome c oxidase
The "second mechanism of respiratory control" (allosteric ATP-inhibition of cytochrome c oxidase (CcO)) is demonstrated for the first time in intact isolated rat liver and heart mitochondria. The problems of measuring the kinetics of allosteric ATP-inhibition in isolated mitochondria we...
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| Format: | Doctoral Thesis |
| Language: | English |
| Published: |
Philipps-Universität Marburg
2010
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| Subjects: | |
| Online Access: | PDF Full Text |
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| Summary: | The "second mechanism of respiratory control" (allosteric ATP-inhibition of
cytochrome c oxidase (CcO)) is demonstrated for the first time in intact isolated rat liver and
heart mitochondria. The problems of measuring the kinetics of allosteric ATP-inhibition in
isolated mitochondria were investigated. And it was found that only at very high ATP/ADP
ratios, this inhibition is obtained and requires an ATP-regenerating system consisting of
phosphoenolpyruvate (PEP) and pyruvate kinase (PK). The allosteric ATP-inhibition can be
switched off probably by dephosphorylation of a serine at CcO subunit-I. The
phosphorylation of CcO at serine, threonine and tyrosine was studied in isolated mitochondria
by extracting complex IV of the respiratory chain (CcO) by BN-PAGE (blue-nativepolyacrylamide-
gel-electrophoresis), SDS-PAGE and Western blotting with the
corresponding antibodies against the phosphorylated amino acids. The extent of allosteric
ATP-inhibition of CcO varied in different preparations of mitochondria, which was suggested
to be based on the psychological situation of the animal at the time of killing. Incubation of
bovine heart tissue slices with insulin decreased the allosteric ATP-inhibition and
phosphorylation of CcO subunit-I at serine. By using a TPP+ (tetraphenylphosphonium)-
electrode, and in collaboration with Katrin Staniek, Veterinary University, Vienna, a
reversible decrease of the mitochondrial membrane potential (DYm) by PEP and PK through
the DYm-independent allosteric ATP-inhibition of CcO at high ATP/ADP ratios was
demonstrated in isolated rat liver mitochondria for the first time. It is proposed that respiration
in living eukaryotic organisms is normally regulated by the DYm-independent ‘allosteric ATPinhibition
of CcO’, and only when the allosteric ATP-inhibition is switched off under stress,
respiration is regulated by ‘respiratory control’, based on DYm according to the Mitchell
Theory. |
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| DOI: | 10.17192/z2010.0635 |