The Unusual Homodimer of a Heme‐Copper Terminal Oxidase Allows Itself to Utilize Two Electron Donors

The heme-copper oxidase superfamily comprises cytochrome c and ubiquinol oxidases. These enzymes catalyze the transfer of electrons from different electron donors onto molecular oxygen. A B-family hyperthermophilic bacterium Aquifex aeolicus was discovered previously to be able use both naphthoquinol as donors. Its mechanism well evolutionary significance are yet unknown. Here we solved its 3.4 Å resolution cryo-microscopic structure a novel dimeric mediated by subunit I (CoxA2) that would essential for binding oxidation. unique structural features in proton oxygen pathways suggest an adaptation this environment. Our results add new conceptual understanding variation oxidases species.