Aim11 is a novel protein involved in the assembly of mitochondrial cytochrome c oxidase

Cytochrome c oxidase (CIV) is the last electron acceptor of the mitochondrial respiratory chain. In yeast, it is composed of 12 subunits, three of which are encoded in the mitochondrial genome. CIV assembly is a modular and highly regulated process that requires several specific factors. In this work, we characterized the role of Aim11 in CIV biogenesis. By high-throughput analysis, it was previously detected that Aim11 interacted with some CIV subunits, but the physiological relevance of these interactions was unknown. In the present work, we found that the{Delta} aim11 mutant exhibited reduced respiratory growth and diminished CIV activity. Using mitochondrial complexome profiling, we detected in the{Delta} aim11 mutant accumulation of intermediates of the three CIV-assembly modules, as well as reduction in supercomplexes levels. Aim11 works together with three other uncharacterized proteins: Mtc3, Gep7, and Iai11. The four proteins form a complex that we named AMIGa (Aim11-Mtc3-Iai11-Gep7 association) complex, necessary for the efficient assembly of CIV. Finally, the human protein TMEM242 was identified as Aim11 orthologue.