c-ring stoichiometry of ATP synthase is adapted to cell physiological requirements of alkaliphilic Bacillus pseudofirmus OF4

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 19; pp. 7874 - 7879
• Main Authors: Preiss, Laura, Klyszejko, Adriana L., Hicks, David B., Liu, Jun, Fackelmayer, Oliver J., Yildiz, Özkan, Krulwich, Terry A., Meier, Thomas
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 07.05.2013; National Acad Sciences
• Subjects: Adenosine triphosphatase; Alanine - chemistry; Amino Acid Motifs; Amino Acid Sequence; Amino acids; Bacillus; Bacillus - enzymology; Bacillus - metabolism; Biochemistry; Bioenergetics; Biological Sciences; Cell growth; Cell Membrane - metabolism; Crystallography; Crystallography, X-Ray; Crystals; Gels; Glycine - chemistry; Gram-positive bacteria; Hydrogen-Ion Concentration; Microscopy, Atomic Force; Mitochondrial Proton-Translocating ATPases - metabolism; Models, Molecular; Mutagenesis, Site-Directed; Mutation; Physiology; Protein Structure, Secondary; Protein Structure, Tertiary; Protons; Stoichiometry; Teeth; F1Fo-ATP synthase rotor; membrane protein complex
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1303333110

The c-rings of ATP synthases consist of individual c-subunits, all of which harbor a conserved motif of repetitive glycine residues (GxGxGxG) important for tight transmembrane α-helix packing. The c-ring stoichiometry determines the number of ions transferred during enzyme operation and has a direct impact on the ion-to-ATP ratio, a cornerstone parameter of cell bioenergetics. In the extreme alkaliphile Bacillus pseudofirmus OF4, the glycine motif is replaced by AxAxAxA. We performed a structural study on two mutants with alanine-to-glycine changes using atomic force microscopy and X-ray crystallography, and found that mutants form smaller c ₁₂ rings compared with the WT c ₁₃. The molar growth yields of B. pseudofirmus OF4 cells on malate further revealed that the c ₁₂ mutants have a considerably reduced capacity to grow on limiting malate at high pH. Our results demonstrate that the mutant ATP synthases with either c ₁₂ or c ₁₃ can support ATP synthesis, and also underscore the critical importance of an alanine motif with c ₁₃ ring stoichiometry for optimal growth at pH >10. The data indicate a direct connection between the precisely adapted ATP synthase c-ring stoichiometry and its ion-to-ATP ratio on cell physiology, and also demonstrate the bioenergetic challenges and evolutionary adaptation strategies of extremophiles.