Identity problems concerning subunits of the membrane factor of the mitochondrial ATPase of Saccharomyces cerevisiae.

As confirmed by fingerprint analysis, high-resolution acrylamide gel electrophoresis identifies subunits of the mitochondrial ATPase complex directly at the level of Coomassie-blue-stained yeast mitochondria. Using this technique, the following results were obtained. 1. Three classes of subunits have been found in the ATPase complex. (a) The classical F1 peptides of cytoribosomal origin (57, 53 and 30.5 kDa). (b) Two peptides of mitoribosomal origin with high cycloheximide-resistant label: one of 7.8 kDa (the OLII gene product), the second of 20 kDa (the OLI2 gene product). Neither of these peptides is readily stained by Coomassie blue in the purified ATPase complex, (c) Four Coomassie-blue-stained peptides (27.5, 25, 23.5 and 22.5 kDa), the last one being subunit 6, which (like class b) functionally qualify as subunits of the membrane factor of the ATPase complex. As shown by labeling with 35SO24- and 3H-labeled amino acids, their biosynthesis is only very slightly cycloheximide-resistant, although it is submitted to coordinate regulation distinct from that of the class F1 peptides. 2. Consequently it was shown that the OLI2 gene product, a 20-kDa peptide with high cycloheximide-resistant label, which was generally taken to be 'subunit 6' of the ATPase, is not in fact identical to this peptide.