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Intrinsic protein kinase activity in mitochondrial oxidative phosphorylation complexes
Darci Phillips1, Angel M Aponte, Raul Covian
1Laboratory of Cardiac Energetics, National Heart, Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, United States.
Biochemistry
|February 19, 2011
Summary
Mitochondrial protein kinases are largely unknown. This study reveals widespread autophosphorylation within mitochondrial complexes, suggesting a novel regulatory mechanism for these protein units.
Area of Science:
- Mitochondrial biology
- Biochemistry
- Cellular metabolism
Background:
- Mitochondrial protein phosphorylation is a key metabolic regulator, but the kinases involved are largely unidentified.
- Detecting mitochondrial kinases is challenging due to low concentrations and antibody limitations.
Purpose of the Study:
- To identify protein kinases within mitochondrial complexes.
- To investigate the role of autophosphorylation in mitochondrial regulation.
Main Methods:
- Utilized blue native gel electrophoresis (BN-PAGE) to isolate rat and porcine heart mitochondrial complexes.
- Screened for protein kinase activity using [γ-(32)P]ATP followed by SDS-PAGE.
- Confirmed findings with Western blots and mass spectrometry.
Main Results:
- Identified widespread protein kinase activity within all five oxidative phosphorylation complexes and citric acid cycle enzymes.
- Detected known pyruvate dehydrogenase (PDH) kinases and phosphatases.
- Found limited evidence for conventional protein kinases, suggesting significant autophosphorylation by mitochondrial proteins themselves.
- Confirmed autophosphorylation in purified Complex V and creatine kinase.
Conclusions:
- Proposes that many mitochondrial complexes possess intrinsic autophosphorylation mechanisms.
- Suggests autophosphorylation plays a functional role in regulating these multiprotein mitochondrial complexes.
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