In the absence of the first membrane-spanning segment of subunit 4(b), the yeast ATP synthase is functional but does not dimerize or oligomerize

• Published in: The Journal of biological chemistry Vol. 277; no. 12; pp. 10739 - 10745
• Main Authors: Soubannier, Vincent, Vaillier, Jacques, Paumard, Patrick, Coulary, Benedicte, Schaeffer, Jacques, Velours, Jean
• Format: Journal Article
• Language: English
• Published: United States 22-03-2002
• Subjects: Adenosine Triphosphatases - metabolism; Amino Acid Sequence; ATP synthase; Cell Membrane - metabolism; Cross-Linking Reagents - pharmacology; Dimerization; Dose-Response Relationship, Drug; Mitochondria - enzymology; Mitochondria - metabolism; Mitochondrial Proton-Translocating ATPases - chemistry; Mitochondrial Proton-Translocating ATPases - metabolism; Molecular Sequence Data; Mutation; Oxygen - metabolism; Phenotype; Phosphorylation; Protein Binding; Protein Structure, Tertiary; Rhodamine 123 - pharmacology; Saccharomyces cerevisiae; Sequence Homology, Amino Acid; Time Factors
• ISSN: 0021-9258
• DOI: 10.1074/jbc.M111882200

The N-terminal portion of the mitochondrial b-subunit is anchored in the inner mitochondrial membrane by two hydrophobic segments. We investigated the role of the first membrane-spanning segment, which is absent in prokaryotic and chloroplastic enzymes. In the absence of the first membrane-spanning segment of the yeast subunit (subunit 4), a strong decrease in the amount of subunit g was found. The mutant ATP synthase did not dimerize or oligomerize, and mutant cells displayed anomalous mitochondrial morphologies with onion-like structures. This phenotype is similar to that of the null mutant in the ATP20 gene that encodes subunit g, a component involved in the dimerization/oligomerization of ATP synthase. Our data indicate that the first membrane-spanning segment of the mitochondrial b-subunit is not essential for the function of the enzyme since its removal did not directly alter the oxidative phosphorylation. It is proposed that the unique membrane-spanning segment of subunit g and the first membrane-spanning segment of subunit 4 interact, as shown by cross-linking experiments. We hypothesize that in eukaryotic cells the b-subunit has evolved to accommodate the interaction with the g-subunit, an associated ATP synthase component only present in the mitochondrial enzyme.