Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 109, Issue 3, Pages 947-952Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1115796109
Keywords
A(1)A(o) ATPase; energy conservation; ion specificity; methanogens; energetic limit
Categories
Funding
- Deutsche Forschungsgemeinschaft [SFB807]
- Biodiversity and Climate Research Centre (BiK-F), Frankfurt am Main
- Ministry of Higher Education, Research, and the Arts (LOEWE)
- Cluster of Excellence Macromolecular Complexes
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ATP synthases are the primary source of ATP in all living cells. To catalyze ATP synthesis, these membrane-associated complexes use a rotary mechanism powered by the transmembrane diffusion of ions down a concentration gradient. ATP synthases are assumed to be driven either by H+ or Na+, reflecting distinct structural motifs in their membrane domains, and distinct metabolisms of the host organisms. Here, we study the methanogenic archaeon Methanosarcina acetivorans using assays of ATP hydrolysis and ion transport in inverted membrane vesicles, and experimentally demonstrate that the rotary mechanism of its ATP synthase is coupled to the concurrent translocation of both H+ and Na+ across the membrane under physiological conditions. Using free-energy molecular simulations, we explain this unprecedented observation in terms of the ion selectivity of the binding sites in the membrane rotor, which appears to have been tuned via amino acid substitutions so that ATP synthesis in M. acetivorans can be driven by the H+ and Na+ gradients resulting from methanogenesis. We propose that this promiscuity is a molecular mechanism of adaptation to life at the thermodynamic limit.
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