The Structure of cbb3 Cytochrome Oxidase Provides Insights into Proton Pumping

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Science  24 Jun 2010:
DOI: 10.1126/science.1187303


The heme-copper-oxidases (HCOs) accomplish the key event of aerobic respiration; they couple O2 reduction and transmembrane proton pumping. To gain new insights into the still enigmatic process, we structurally characterized a C-family HCO—essential for the pathogenicity of many bacteria—which differs from the two other HCO families, A and B, that have been structurally analyzed. The x-ray structure of the C-family cbb3 oxidase from Pseudomonas stutzeri at 3.2 Å resolution shows an electron supply system different from families A and B. Like family B HCOs, C HCOs have only one pathway, which conducts protons via an alternative tyrosine-histidine crosslink. Structural differences around hemes b and b3 suggest a different redox-driven proton pumping mechanism and provide clues to explain the higher activity of family C HCOs at low oxygen concentrations.