Cryo-EM structure of respiratory complex IV.

In fungi, the mitochondrial respiratory chain complexes (complexes I-IV) are responsible for oxidative phosphorylation, as in higher eukaryotes. Cryo-EM was used to identify a 200 kDa membrane protein from in lipid nanodiscs as cytochrome oxidase (complex IV) and its structure was determined at 5.5 Å resolution. The map closely resembles the cryo-EM structure of complex IV from . Its ten subunits are conserved in and , but other transmembrane subunits are missing. The different structure of the Cox5a subunit is typical for fungal complex IV and may affect the interaction with complex III in a respiratory supercomplex. Additional density was found between the matrix domains of the Cox4 and Cox5a subunits that appears to be specific to .