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    Rcf2 revealed in cryoEM structures of hypoxic isoforms of mature mitochondrial III-IV supercomplexes

    Hartley, Andrew and Meunier, B. and Pinotsis, Nikos and Marechal, Amandine (2020) Rcf2 revealed in cryoEM structures of hypoxic isoforms of mature mitochondrial III-IV supercomplexes. Proceedings of the National Academy of Sciences of the United States of America 117 (17), pp. 9329-9337. ISSN 0027-8424.

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    The organisation of the mitochondrial electron transport chain proteins into supercomplexes (SCs) is now undisputed, however their assembly process, or the role of differential expression isoforms, have yet to be determined. In Saccharomyces cerevisiae, cytochrome c oxidase (CIV) forms SCs of varying stoichiometry with cytochrome bc1 (CIII). Recent studies have revealed, in normoxic condition of growth, an interface made exclusively by Cox5A, the only yeast respiratory protein that exists as one of two isoforms depending on oxygen levels. Here, we present the cryo-EM structures of the III2-IV1 and III2-IV2 SCs containing the hypoxic isoform Cox5B solved at 3.4 and 2.8 Å, respectively. We show that the change of isoform doesn’t affect SC formation or activity and that SC stoichiometry is dictated by the level of CIII/CIV biosynthesis. Comparison of the CIV5B and CIV5A-containing SC structures highlighted few differences, mainly found in the region of Cox5. Additional density was revealed in all SCs, independent of CIV isoform, in a pocket formed by Cox1, Cox3, Cox12 and Cox13, away from the CIII-CIV interface. In the CIV5B-containing hypoxic SCs, this could be confidently assigned to the hypoxia-induced gene 1 (Hig1) type 2 protein Rcf2. With conserved residues in mammalian Hig1 proteins and Cox3/Cox12/Cox13 orthologues, we propose that Hig1 type 2 proteins are stoichiometric subunits of CIV, at least when within a III-IV SC.


    Item Type: Article
    Additional Information: This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND). The press embargo will lift on April 6, 2020 at 3:00 PM U.S. Eastern time. The embargo date is the earliest possible date that your article can publish.
    School: Birkbeck Faculties and Schools > Faculty of Science > School of Natural Sciences
    Research Centres and Institutes: Structural Molecular Biology, Institute of (ISMB)
    Depositing User: Amandine Marechal
    Date Deposited: 16 Apr 2020 13:32
    Last Modified: 02 Aug 2023 17:59


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