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. 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. Binds to the mature mitochondrial complex III dimer, after the incorporation of the Rieske protein (UQCRFS1). Interacts with UQCRC1 and UQCRFS1 (By similarity). Interacts with ZFYVE26 and CHMP4B. Belongs to the TTC19 family. Extended N-terminus.