Angewandte Chemie International Edition, 4 March, 2021, DOI：https://doi.org/10.1002/anie.202016785
The unusual homodimer of a heme‐copper terminal oxidase allows itself to utilize two electron donors
Yun Zhu, Guoliang Zhu, Hui Zeng, Shuangbo Zhang, Jana Juli, Linhua Tai, Danyang Zhang, Xiaoyun Pang, Yan Zhang, Sin Man Lam, Guohong Peng, Hartmut Michel, Fei Sun
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 cytochrome c oxidase from the hyperthermophilic bacterium Aquifex aeolicus was discovered previously to be able to use both cytochrome c and naphthoquinol as electron donors. Its molecular mechanism as well as the evolutionary significance are yet unknown. Here we solved its 3.4 angstrom resolution electron cryo‐microscopic structure and discovered a novel dimeric structure mediated by subunit I (CoxA2) that would be essential for naphthoquinol binding and oxidation. The unique structural features in both proton and oxygen pathways suggest an evolutionary adaptation of this oxidase to its hyperthermophilic environment. Our results add a new conceptual understanding of structural variation of cytochrome c oxidases in different species.