Activation and stiffness of the inhibited states of F1-ATPase probed by single-molecule manipulation.
F(1)-ATPase (F(1)), a soluble portion of F(o)F(1)-ATP synthase (F(o)F(1)), is an ATP-driven motor in which gammaepsilon subunits rotate in the alpha(3)beta(3) cylinder. Activity of F(1) and F(o)F(1) from Bacillus PS3 is attenuated by the epsilon subunit in an inhibitory extended form. In this study we observed ATP-dependent transition of epsilon in single F(1) molecules from extended form to hairpin form by fluorescence resonance energy transfer. The results justify the previous bulk experiments and ensure that fraction of F(1) with hairpin epsilon directly determines the fraction of active F(1) at any ATP concentration. Next, mechanical activation and stiffness of epsilon-inhibited F(1) were examined by the forced rotation of magnetic beads attached to gamma. Compared with ADP inhibition, which is another manner of inhibition, rotation by a larger angle was required for the activation from epsilon inhibition when the beads were forced to rotate to ATP hydrolysis direction, and more torque was required to reach the same rotation angle when beads were forced to rotate to ATP synthesis direction. The results imply that if F(o)F(1) is resting in the epsilon-inhibited state, F(o) motor must transmit to gamma a torque larger than expected from thermodynamic equilibrium to initiate ATP synthesis.
ICORP ATP Synthesis Regulation Project, Japan Science and Technology Corporation, Aomi 2-3-6, Tokyo 135-0064, Japan.
Ei-ichiro
E
Saita
Ryota
R
Iino
Toshiharu
T
Suzuki
Boris A
BA
Feniouk
Kazuhiko
K
Kinosita
Masasuke
M
Yoshida
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry* / Q000378:metabolism; D001407:Bacillus / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry; D004926:Escherichia coli / Q000201:enzymology; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000494:pharmacology; D006868:Hydrolysis; D008954:Models, Biological; D020409:Molecular Motor Proteins / Q000737:chemistry; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D013314:Stress, Mechanical
D005456:Fluorescent Dyes; D020409:Molecular Motor Proteins; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases; D003545:Cysteine