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Updated: Aug 24, 2026

Inner Mitochondrial Membrane Sensitivity to Na+ Reveals Partially Segmented Functional CoQ Pools
Published on: July 20, 2022
Regulation of NADH/CoQ oxidoreductase: do phosphorylation events affect activity?
Mary C Maj1, Sandeep Raha, Tomoko Myint
1Metabolic Research Programme, The Hospital for Sick Children, 555 University Avenue, Toronto M5G 1X8, Canada.
Abstract:
We had previously suggested that phosphorylation of proteins by mitochondrial kinases regulate the activity of NADH/CoQ oxidoreductase. Initial data showed that pyruvate dehydrogenase kinase (PDK) and cAMP-dependent protein kinase A (PKA) phosphorylate mitochondrial membrane proteins. Upon phosphorylation with crude PDK, mitochondria appeared to be deficient in NADH/cytochrome c reductase activity associated with increased superoxide production. Conversely, phosphorylation by PKA resulted in increased NADH/cytochrome c reductase activity and decreased superoxide formation. Current data confirms PKA involvement in regulating Complex I activity through phosphorylation of an 18 kDa subunit. Beef heart NADH/ cytochrome c reductase activity increases to 150% of control upon incubation with PKA and ATP-gamma-S. We have cloned the four human isoforms of PDK and purified beef heart Complex I. Incubation of mitochondria with PDK isoforms and ATP did not alter Complex I activity or superoxide production. Radiolabeling of mitochondria and purified Complex I with PDK failed to reveal phosphorylated proteins.
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