Accessory subunits are integral for assembly and function of human mitochondrial complex I David A. Stroud1*, Elliot E. Surgenor1, Luke E. Formosa1,2, Boris Reljic2†, Ann E. Frazier3,4, Marris G. Dibley1, Laura D. Osellame1, Tegan Stait3, Traude H. Beilharz1, David R. Thorburn3-5, Agus Salim6, Michael T. Ryan1* 1Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, 3800, Melbourne, Australia. 2Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University 3086, Melbourne, Australia. 3Murdoch Childrens Research Institute, Royal Children’s Hospital, Melbourne 3052, Australia 4Department of Pediatrics, University of Melbourne, Melbourne 3052, Australia. 5Victorian Clinical Genetics Services, Royal Children’s Hospital 3052, Melbourne, Australia. 6Department of Mathematics and Statistics, La Trobe University 3086, Melbourne Australia. *Correspondence to:
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[email protected] †Current address: Walter and Eliza Hall Institute of Medical Research, Parkville, Melbourne, Victoria 3052, Australia Complex I (NADH:ubiquinone oxidoreductase) is the first enzyme of the mitochondrial respiratory chain (RC) and is composed of 44 different subunits in humans, making it one of the largest known multi-subunit membrane protein complexes1. Complex I exists in supercomplex forms with RC complexes III and IV, which are together required for the generation of a transmembrane proton gradient used for the synthesis of ATP2. Complex I is also a major source of damaging reactive oxygen species and its dysfunction is associated with mitochondrial disease, Parkinson’s disease and aging3-5. Bacterial and human complex I share 14 core subunits essential for enzymatic function, however the role and requirement of the remaining 31 human accessory subunits is unclear1,6.