Perfect chemomechanical coupling of FoF1-ATP synthase
Naoki Soga a,1, Kazuya Kimura a, Kazuhiko Kinosita, Jr. a, Masasuke Yoshida b, and Toshiharu Suzuki a,b,1,2
Author Affiliations
a Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan;
b Department of Molecular Bioscience, Kyoto Sangyo University, Kyoto 603-8555, Japan
Edited by Pierre A. Joliot, Institut de Biologie Physico-Chimique, Paris, France, and approved April 4, 2017 (received for review January 20, 2017)
Source/Fonte: “ATP Synthase: The Power Plant of the Cell.”
Significance
Peter D. Mitchell, a Nobel awardee in 1978, proposed that FoF1-ATP synthase converts energy between electrochemical potential of H+ across biological membrane (Δμ∼H+Δμ∼H+), which is established by respiratory chain complexes, and chemical potential of adenine nucleotide [ΔG(ATP)]. However, the efficiency of the energy conversion has been a matter of debate for over 50 years. In this study, with a highly reproducible analytical system using FoF1-ATP synthase from thermophilic Bacillus, apparently perfect energy conversion was observed. Mitchell’s prediction thus has quantitative evidence.
Abstract
FoF1-ATP synthase (FoF1) couples H+ flow in Fo domain and ATP synthesis/hydrolysis in F1 domain through rotation of the central rotor shaft, and the H+/ATP ratio is crucial to understand the coupling mechanism and energy yield in cells. Although H+/ATP ratio of the perfectly coupling enzyme can be predicted from the copy number of catalytic β subunits and that of H+ binding c subunits as c/β, the actual H+/ATP ratio can vary depending on coupling efficiency. Here, we report actual H+/ATP ratio of thermophilic Bacillus FoF1, whose c/β is 10/3. Proteoliposomes reconstituted with the FoF1 were energized with ΔpH and Δψ by the acid−base transition and by valinomycin-mediated diffusion potential of K+ under various [ATP]/([ADP]⋅[Pi]) conditions, and the initial rate of ATP synthesis/hydrolysis was measured. Analyses of thermodynamically equilibrated states, where net ATP synthesis/hydrolysis is zero, show linear correlation between the chemical potential of ATP synthesis/hydrolysis and the proton motive force, giving the slope of the linear function, that is, H+/ATP ratio, 3.3 ± 0.1. This value agrees well with the c/β ratio. Thus, chemomechanical coupling between Fo and F1 is perfect.
FoF1-ATP synthase chemiosmotic coupling theory ATPase proton motive force electrochemical potential
Footnotes
1 Present address: Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
2 To whom correspondence should be addressed. Email: toshisuz@appchem.t.u-tokyo.ac.jp.
Author contributions: N.S., K. Kinosita, M.Y., and T.S. designed research; N.S. and K. Kimura performed research; N.S. and T.S. analyzed data; and N.S., M.Y., and T.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1700801114/-/DCSupplemental.
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NOTA DESTE BLOGGER:
Os autores usaram a palavra "perfect" treze vezes no artigo, o que é incomum em artigos científicos, mas esses japoneses ousaram seguir a evidência aonde ela os estava levando: complexidade absurda que o mero acaso e a fortuita necessidade não conseguem explicar. Restou o que? Design Inteligente!!!
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