Yeast mitochondrial F1F0-ATP synthase exists as a dimer: identification of three dimer-specific subunits.

Using the technique of blue native gel electrophoresis, the oligomeric state of the yeast mitochondrial F1F0-ATP synthase was analysed. Solubilization of mitochondrial membranes with low detergent to protein ratios led to the identification of the dimeric state of the ATP synthase. Analysis of the subunit composition of the dimer, in comparison with the monomer, revealed the presence of three additional small proteins. These dimer-specific subunits of the ATP synthase were identified as the recently described subunit e/Tim11 (Su e/Tim11), the putative subunit g homolog (Su g) and a new component termed subunit k (Su k). Although, as shown here, these three proteins are not required for the formation of enzymatically active ATP synthase, Su e/Tim11 and Su g are essential for the formation of the dimeric state. Su e/Tim11 appears to play a central role in this dimerization process. The dimer-specific subunits are associated with the membrane bound F0-sector. The F0-sector may thereby be involved in the dimerization of two monomeric F1F0-ATP synthase complexes. We speculate that the F1F0-ATP synthase of yeast, like the other complexes of oxidative phosphorylation, form supracomplexes to optimize transduction of energy and to enhance the stability of the complex in the membrane.