Chemomechanical coupling in single-molecule F-type ATP synthase.
An extremely small reaction chamber with a volume of a few femtoliters was developed for a highly sensitive detection of biological reaction. By encapsulating a single F(1)-ATPase (F(1)) molecule with ADP and an inorganic phosphate in the chamber, the chemomechanical coupling efficiency of ATP synthesis catalyzed by reversely rotated F(1) was successfully determined (Rondelez et al., 2005a, Nature, 444, 773-777). While the alpha3beta3gamma subcomplex of F(1) generated ATP with a low efficiency (approximately 10%), inclusion of the epsilon subunit into the subcomplex enhanced the efficiency up to 77%. This raises a new question about the mechanism of F(0)F(1)-ATP synthase (F(0)F(1)): How does the epsilon subunit support the highly coupled ATP synthesis of F(1)? To address this question, we measured the conformational dynamics of the epsilon subunit using fluorescence resonance energy transfer (FRET) at the single-molecule level. The experimental data revealed epsilon changes the conformation of its C-terminus helices in a nucleotide-dependent manner. It is plausible that the conformational change of epsilon switches the catalytic mode of F(0)F(1) for highly coupled ATP synthesis.
Iino
Ryota
R
The Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan.
Rondelez
Yannick
Y
Yoshida
Masasuke
M
Noji
Hiroyuki
H
D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D001426:Bacterial Proteins / Q000737:chemistry; D001696:Biomechanical Phenomena; D020409:Molecular Motor Proteins / Q000737:chemistry; D011487:Protein Conformation; D021122:Protein Subunits; D011506:Proteins / Q000737:chemistry; D006180:Proton-Translocating ATPases / Q000737:chemistry*; D000097795:ATPase Inhibitory Protein
D000255:Adenosine Triphosphate; D001426:Bacterial Proteins; D020409:Molecular Motor Proteins; D021122:Protein Subunits; D011506:Proteins; D006180:Proton-Translocating ATPases; D000097795:ATPase Inhibitory Protein