Oxa1p

Oxa1p is a mitochondrial inner membrane protein in the yeast Saccharomyces cerevisiae. It is the core component of the Oxa1 complex, a conserved membrane protein insertase related to the bacterial YidC family. Oxa1p mediates the insertion and assembly of polypeptides into the inner mitochondrial membrane, supporting the biogenesis of the respiratory chain.

In yeast, Oxa1p associates with the mitochondrial ribosome via accessory factors such as Mba1, enabling cotranslational insertion of mitochondrially encoded subunits. Substrates include subunits of the respiratory chain complexes, notably those encoded by the mitochondrial genome, such as cytochrome c oxidase components, and other membrane proteins essential for mitochondrial function. Oxa1p also contributes to the assembly and organization of respiratory chain supercomplexes and is involved in the maturation of some other mitochondrial membrane proteins, including certain ATP synthase subunits.

Oxa1p is encoded by the OXA1 gene and is evolutionarily conserved across eukaryotes. Its bacterial counterpart YidC is functionally related, highlighting a conserved strategy for membrane protein insertion that originated in bacteria and was retained in mitochondria. Disruption of Oxa1p function impairs respiratory chain assembly and mitochondrial respiration, leading to growth defects on nonfermentable carbon sources in yeast and broader mitochondrial dysfunction when conserved pathways are compromised.

Studies of Oxa1p illuminate the mechanism of membrane protein insertion in mitochondria and the coordination between mitochondrial translation and membrane integration, illustrating how a bacterial-derived insertase supports organellar biogenesis and energy metabolism.