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Mitochondrial COA7 is a heme-binding protein with disulfide reductase activity, which acts in the early stages of complex IV assembly

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posted on 2022-05-20, 04:04 authored by LE Formosa, S Maghool, AJ Sharpe, B Reljic, L Muellner-Wong, DA Stroud, MT Ryan, Megan MaherMegan Maher
Cytochrome c oxidase (COX) assembly factor 7 (COA7) is a metazoan-specific assembly factor, critical for the biogenesis of mitochondrial complex IV (cytochrome c oxidase). Although mutations in COA7 have been linked to complex IV assembly defects and neurological conditions such as peripheral neuropathy, ataxia, and leukoencephalopathy, the precise role COA7 plays in the biogenesis of complex IV is not known. Here, we show that loss of COA7 blocks complex IV assembly after the initial step where the COX1 module is built, progression from which requires the incorporation of copper and addition of the COX2 and COX3 modules. The crystal structure of COA7, determined to 2.4 Å resolution, reveals a banana-shaped molecule composed of five helix-turn-helix (α/α) repeats, tethered by disulfide bonds. COA7 interacts transiently with the copper metallochaperones SCO1 and SCO2 and catalyzes the reduction of disulfide bonds within these proteins, which are crucial for copper relay to COX2. COA7 binds heme with micromolar affinity, through axial ligation to the central iron atom by histidine and methionine residues. We therefore propose that COA7 is a heme-binding disulfide reductase for regenerating the copper relay system that underpins complex IV assembly.


This study was funded by the Australian Research Council (DP140102746 and FT180100397 to M.J.M. and DP220102030 to M.J.M. and M.T.R.) , the National Health and Medical Research Council (GNT1165217 to M.T.R. and M.J.M., GNT1140906 and GNT1140851 to D.A.S., and GNT2010149 to L.E.F.) , and an Australian Government Research Training Program Scholarship to S.M. L.E.F. also acknowledges support from the Mito Foundation. Part of this study was carried out using the MX2 beamline at the Australian Synchrotron, which is part of the Australian Nuclear Science and Technology Organisation (ANSTO) , and made use of the Australian Cancer Research Foundation (ACRF) detector. We thank the beamline staff for their enthusiastic and professional support, Dr. Yee-Foong Mok at the Melbourne Protein characterization facility, the Bio21 Molecular Science and Biotechnol-ogy Institute for performing the AUC experiments and data analyses, the Bio21 Mass Spectrometry and Proteomics Facility for the provision of instru-mentation, training, and technical support, Daniel Machell for PyMOL and coding assistance, Dr. Katie Ganio and Prof. Christopher McDevitt for the ICP-MS analysis, and Mrs. Mahnaz Dideh Var for her extraordinary support with the structural biology aspects of this study. We thank the reviewers for their constructive comments. Schematics were created using .


Publication Date



Proceedings of the National Academy of Sciences of the United States of America





Article Number





National Academy of Science



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© The authors. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).