Probably involved in the biogenesis of the COX complex. Lethal at larval stage (PubMed:16172499). Larvae show reduced locomotor speed and response to light (PubMed:16172499). Results in smaller muscle fibers with mitochondria defects (PubMed:16172499). RNAi-mediated knockdown is lethal at larval stage (PubMed:25164807). RNAi-mediated knockdown in the developing CNS, in the eye and antenna disk from early larval stages shows increased lifespan with reduction of COX activity, increased succinate dehydrogenase (SDH) activity, reduced locomotor speed and response to light (PubMed:16172499, PubMed:25164807). RNAi-mediated knockdown in mesodermal derivatives from early embryonic stages to pupal metamorphosis is lethal at pupal stage with muscles showing enlarged and disorganized mitochondria and reduced activity of all mitochondrial respiratory chain complexes (PubMed:25164807). Belongs to the SURF1 family.