The function of TMEM223 (transmembrane protein 223, ENSG00000168569) is as follows. Mitochondrial ribosome-associated protein involved in the first steps of cytochrome c oxidase complex (complex IV) biogenesis (PubMed:34969438). Stimulates the translation of MT-CO1 mRNA and is a constituent of early MT-CO1 assembly intermediates (PubMed:34969438). .