Mutations which decouple the proton pump of the cytochrome c oxidase from Rhodobacter sphaeroides perturb the environment of glutamate 286

Mutants that decouple the proton pump of cytochrome c oxidase from Rhodobacter sphaeroides are postulated to do so by increasing the pKa of glutamate 286, which is 20 Å away. The possibility that a conformational change near E286 is induced by the decoupling mutations (N139D and N207D) was investigated by FTIR difference spectroscopy. In both decoupled mutants, the reduced-minus-oxidized FTIR difference spectra show a shift of 2 cm−1 to lower frequency of the band resulting from the absorbance of E286 in the oxidized enzyme. The decoupling mutants may influence E286 by altering the chain of water molecules which runs from the site of the mutations to E286.