title: Stabilization of the peroxy intermediate in the oxygen splitting reaction of cytochrome cbb(3).
abstract: The proton-pumping cbb(3)-type cytochrome c oxidases catalyze cell respiration in many pathogenic bacteria. For reasons not yet understood, the apparent dioxygen (O(2)) affinity in these enzymes is very high relative to other members of the heme-copper oxidase (HCO) superfamily. Based on density functional theory (DFT) calculations on intermediates of the oxygen scission reaction in active-site models of cbb(3)- and aa(3)-type oxidases, we find that a transient peroxy intermediate (I(P), Fe[III]-OOH(-)) is ~6kcal/mol more stable in the former case, resulting in more efficient kinetic trapping of dioxygen and hence in a higher apparent oxygen affinity. The major molecular basis for this stabilization is a glutamate residue, polarizing the proximal histidine ligand of heme b(3) in the active site.
authors.affiliation: University of Helsinki, Helsinki, Finland. vivek.sharma@helsinki.fi
authors.forename: Vivek
authors.initials: V
authors.lastname: Sharma
authors.forename: Mårten
authors.initials: M
authors.lastname: Wikström
authors.forename: Ville R I
authors.initials: VR
authors.lastname: Kaila
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D020134:Catalytic Domain; D003300:Copper / Q000737:chemistry; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000737:chemistry / Q000378:metabolism; D008962:Models, Theoretical; D015394:Molecular Structure; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry*; D055672:Static Electricity
chemical_list: D001426:Bacterial Proteins; D003300:Copper; D010088:Oxidoreductases; C020094:duroquinol oxidase; D006419:Heme Oxygenase (Decyclizing); C414443:cbb3 oxidase; D003576:Electron Transport Complex IV; D010100:Oxygen