The Redox-Bohr group associated with iron-sulfur cluster N2 of complex I.
Proton pumping respiratory complex I (NADH:ubiquinone oxidoreductase) is a major component of the oxidative phosphorylation system in mitochondria and many bacteria. In mammalian cells it provides 40% of the proton motive force needed to make ATP. Defects in this giant and most complicated membrane-bound enzyme cause numerous human disorders. Yet the mechanism of complex I is still elusive. A group exhibiting redox-linked protonation that is associated with iron-sulfur cluster N2 of complex I has been proposed to act as a central component of the proton pumping machinery. Here we show that a histidine in the 49-kDa subunit that resides near iron-sulfur cluster N2 confers this redox-Bohr effect. Mutating this residue to methionine in complex I from Yarrowia lipolytica resulted in a marked shift of the redox midpoint potential of iron-sulfur cluster N2 to the negative and abolished the redox-Bohr effect. However, the mutation did not significantly affect the catalytic activity of complex I and protons were pumped with an unchanged stoichiometry of 4 H(+)/2e(-). This finding has significant implications on the discussion about possible proton pumping mechanism for complex I.
Zwicker
Klaus
K
Universität Frankfurt, Zentrum der Biologischen Chemie, Molekulare Bioenergetik, D-60590 Frankfurt am Main, Germany.
Galkin
Alexander
A
Dröse
Stefan
S
Grgic
Ljuban
L
Kerscher
Stefan
S
Brandt
Ulrich
U
D042967:Electron Transport Complex I / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008715:Methionine / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010766:Phosphorylation; D011487:Protein Conformation; D011522:Protons; D025062:Yarrowia / Q000201:enzymology
D007506:Iron-Sulfur Proteins; D011522:Protons; D008715:Methionine; D042967:Electron Transport Complex I; D010100:Oxygen