Mutations in the mitochondrially encoded cytochrome c assembly factor COX10 cause Leigh’s disease, a mitochondrial encephalopathy [21], while NDUFV1 is the largest (75 kDa) subunit of complex I. These data suggest that mitochondrial function is critical for maintaining proteostasis during aging, and further that abnormal proteostasis might contribute to the pathogenesis of mitochondrial encephalomyopathies. The gene discussed is COX10; the disease is Leigh syndrome.