Identification of the mitochondrial ND3 subunit as a structural component involved in the active/deactive enzyme transition of respiratory complex I.
Mitochondrial complex I (NADH:ubiquinone oxidoreductase) undergoes reversible deactivation upon incubation at 30-37 degrees C. The active/deactive transition could play an important role in the regulation of complex I activity. It has been suggested recently that complex I may become modified by S-nitrosation under pathological conditions during hypoxia or when the nitric oxide:oxygen ratio increases. Apparently, a specific cysteine becomes accessible to chemical modification only in the deactive form of the enzyme. By selective fluorescence labeling and proteomic analysis, we have identified this residue as cysteine-39 of the mitochondrially encoded ND3 subunit of bovine heart mitochondria. Cysteine-39 is located in a loop connecting the first and second transmembrane helix of this highly hydrophobic subunit. We propose that this loop connects the ND3 subunit of the membrane arm with the PSST subunit of the peripheral arm of complex I, placing it in a region that is known to be critical for the catalytic mechanism of complex I. In fact, mutations in three positions of the loop were previously reported to cause Leigh syndrome with and without dystonia or progressive mitochondrial disease.
Galkin
Alexander
A
Molecular Bioenergetics Group, Cluster of Excellence Frankfurt Macromolecular complexes, Medical School, Johann Wolfgang Goethe-Universität, Theodor-Stern-Kai 7, Frankfurt am Main, Germany.
Meyer
Björn
B
Wittig
Ilka
I
Karas
Michael
M
Schägger
Hermann
H
Vinogradov
Andrei
A
Brandt
Ulrich
U
D000818:Animals; D002384:Catalysis; D002417:Cattle; D002918:Chymotrypsin / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry*; D042967:Electron Transport Complex I / Q000737:chemistry* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005456:Fluorescent Dyes / Q000494:pharmacology; D013058:Mass Spectrometry / Q000379:methods; D028361:Mitochondrial Diseases / Q000378:metabolism; D008954:Models, Biological; D009206:Myocardium / Q000378:metabolism; D009569:Nitric Oxide / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D040901:Proteomics / Q000379:methods
D005456:Fluorescent Dyes; D009569:Nitric Oxide; D002918:Chymotrypsin; D042967:Electron Transport Complex I; D003545:Cysteine; D010100:Oxygen