Cytochrome c oxidase (COX) or Complex IV (CIV), the terminal enzyme of the mitochondrial respiratory chain, is a copper-heme A oxidase. Human COX is composed of 14 subunits of dual genetic origin. The three subunits forming the COX catalytic core (COX1, COX2 and COX3) are encoded in the mitochondrial DNA and the rest are encoded in the nuclear DNA. COX biogenesis is a highly regulated process that requires the assistance of more than 30 nucleus-encoded assembly factors. They promote all steps of the assembly process, including the maturation of catalytic subunits by formation of their metal centers (CuA in COX2 and heme a and heme a3-CuB in COX1) and the formation of assembly intermediates. COX metallation has received biomedical attention because mutations in COX specific copper chaperones result in fatal cardio- or encephalo-myopathies. Here we have investigated the function in human cells of the cardiomyopathy protein PET191. PET191 is a conserved twin-CX9C protein, located in the intermembrane space, which is required for COX assembly in a capacity that remains unknown. Our preliminary data has linked PET191 function to the assembly of the copper center in COX1, a poorly characterized pathway in human cells. In yeast and bacteria, the protein COX11 is the only and essential COX1-specific copper chaperone. To gain insight into maturation of CuB center in human COX1 we have used the gene-editing TALEN technology and Crispr/Cas9 to create cells lines knock-out for COX11, PET191 and COX19, another small conserved CX9C protein connected with function of COX11 in yeast. Our preliminary data suggest a model in which PET191 could cooperate with COX11 and COX19 to build the CuB site in human COX1.

Additional author(s): Antoni Barrientos