Assembly of respiratory complexes I, III, and IV into NADH oxidase supercomplex stabilizes complex I in Paracoccus denitrificans.
Stable supercomplexes of bacterial respiratory chain complexes III (ubiquinol:cytochrome c oxidoreductase) and IV (cytochrome c oxidase) have been isolated as early as 1985 (Berry, E. A., and Trumpower, B. L. (1985) J. Biol. Chem. 260, 2458-2467). However, these assemblies did not comprise complex I (NADH:ubiquinone oxidoreductase). Using the mild detergent digitonin for solubilization of Paracoccus denitrificans membranes we could isolate NADH oxidase, assembled from complexes I, III, and IV in a 1:4:4 stoichiometry. This is the first chromatographic isolation of a complete "respirasome." Inactivation of the gene for tightly bound cytochrome c552 did not prevent formation of this supercomplex, indicating that this electron carrier protein is not essential for structurally linking complexes III and IV. Complex I activity was also found in the membranes of mutant strains lacking complexes III or IV. However, no assembled complex I but only dissociated subunits were observed following the same protocols used for electrophoretic separation or chromatographic isolation of the supercomplex from the wild-type strain. This indicates that the P. denitrificans complex I is stabilized by assembly into the NADH oxidase supercomplex. In addition to substrate channeling, structural stabilization of a membrane protein complex thus appears as one of the major functions of respiratory chain supercomplexes.
Stroh
Anke
A
Zentrum der Biologischen Chemie, Universitätsklinikum Frankfurt, D-60590 Frankfurt, Germany.
Anderka
Oliver
O
Pfeiffer
Kathy
K
Yagi
Takao
T
Finel
Moshe
M
Ludwig
Bernd
B
Schägger
Hermann
H
D045222:Electron Transport Chain Complex Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D042967:Electron Transport Complex I / Q000737:chemistry / Q000378:metabolism; D014450:Electron Transport Complex III / Q000737:chemistry / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism; D004795:Enzyme Stability; D005798:Genes, Bacterial; D007700:Kinetics; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry / Q000378:metabolism; D010231:Paracoccus denitrificans / Q000201:enzymology* / Q000235:genetics
D045222:Electron Transport Chain Complex Proteins; D009097:Multienzyme Complexes; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D003576:Electron Transport Complex IV; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III