Required for the preservation of the structural and functional integrity of mitochondrial respiratory complex III by allowing the physiological turnover of the Rieske protein UQCRFS1 (PubMed:21278747, PubMed:28673544). Involved in the clearance of UQCRFS1 N-terminal fragments, which are produced upon incorporation into the complex III and whose presence is detrimental for its catalytic activity (PubMed:28673544). Binds to the mature mitochondrial complex III dimer, after the incorporation of the Rieske protein UQCRFS1 (PubMed:28673544, PubMed:21278747). Interacts with UQCRC1 and UQCRFS1 (PubMed:21278747). Interacts with ZFYVE26 and CHMP4B (By similarity). Mutant mice show progressive neurological and energy metabolic decline, decrease complex III activity, increased production of reactive oxygen species, extensive astrogliosis and accumulation of ubiquitinated proteins in neurons of the thalamus. Compatible with a Mendelian autosomal recessive trait. No evidence of embryonic lethality nor evidence of obvious neuronal loss. Belongs to the TTC19 family. Truncated N-terminus.