Structural changes at the surface of cytochrome c oxidase alter the proton-pumping stoichiometry.

ABSTRACT: Data from earlier studies showed that minor structural changes at the surface of cytochrome c oxidase, in one of the proton-input pathways (the D pathway), result in dramatically decreased activity and a lower proton-pumping stoichiometry. To further investigate how changes around the D pathway orifice influence functionality of the enzyme, here we modified the nearby C-terminal loop of subunit I of the Rhodobacter sphaeroides cytochrome c oxidase. Removal of 16 residues from this flexible surface loop resulted in a decrease in the proton-pumping stoichiometry to <50% of that of the wild-type enzyme. Replacement of the protonatable residue Glu552, part of the same loop, by an Ala, resulted in a similar decrease in the proton-pumping stoichiometry without loss of the O₂-reduction activity or changes in the proton-uptake kinetics. The data show that minor structural changes at the orifice of the D pathway, at a distance of ~40?Å from the proton gate of cytochrome c oxidase, may alter the proton-pumping stoichiometry of the enzyme.

SUBMITTER: Berg J 

PROVIDER: S-EPMC6943178 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature