atrophy, generalized muscle hypotonia, hyperostosis, yellowish sclera associated with mild indirect hyperbilirubinemia, impaired coagulation functions, elevated LDH, alanine, and bilirubin, and reduced vitamin E levels. A homozygous mutation, E138K, has been found to result in reduced COX4I2 expression (25% in fibroblasts) and an impaired response to hypoxia. Functional COX4I2 expression below 40% of its normal level is predicted to be rate-limiting, with the E138K mutation occurring in what is believed to be a highly conserved residue of subunit IV. Interactions COX4I2 has been shown to interact with Cytochrome c (CYCS). Additionally, APP, COA3, and KRAS have been found to have protein-protein interactions with COX4I2. References External links Further reading