The largest mitochondrial translation product copurifying with the mitochondrial adenosine triphosphatase of Saccharomyces cerevisiae is not a subunit of the enzyme complex.

Mitochondrial adenosine triphosphatase isolated from a double mutant of Saccharomyces cerevisiae lacking cytochrome b apoprotein and subunit II of cytochrome oxidase does not contain the mitochondrial translation product (approximate molecular weight, 32,000) previously suggested to be a subunit of the enzyme complex.