Torque Generation in F1-ATPase Devoid of the Entire Amino-Terminal Helix of the Rotor That Fills Half of the Stator Orifice

Ayako kohori†◊,  Ryohei Chiwata†◊,  Mohammad Delawar Hossain†‡,  Shou Furuike†,  Katsyuki Shiroguchi†,  Kengo Adachi†,  Masasuke Yoshida§¶ and  Kazuhiko Kinosita†*

Journal name:  Biophysical Jornal
Volume:  101
Page:  188-195
doi: 10.1016/j.bpj.2011.05.008
Received 
Accepted 

Abstract

F1-ATPase is an ATP-driven rotary molecular motor in which the central γ-subunit rotates inside a cylinder made of α3β3 subunits. The amino and carboxyl termini of the γ rotor form a coiled coil of α-helices that penetrates the stator cylinder to serve as an axle. Crystal structures indicate that the axle is supported by the stator at two positions, at the orifice and by the hydrophobic sleeve surrounding the axle tip. The sleeve contacts are almost exclusively to the longer carboxyl-terminal helix, whereas nearly half the orifice contacts are to the amino-terminal helix. Here, we truncated the amino-terminal helix stepwise up to 50 residues, removing one half of the axle all the way up and far beyond the orifice. The half-sliced axle still rotated with an unloaded speed a quarter of the wild-type speed, with torque nearly half the wild-type torque. The truncations were made in a construct where the rotor tip was connected to a β-subunit via a short peptide linker. Linking alone did not change the rotational characteristics significantly. These and previous results show that nearly half the normal torque is generated if rotor-stator interactions either at the orifice or at the sleeve are preserved, suggesting that the make of the motor is quite robust.

Affiliations

† Department of Physics, Faculty of Science and Engineering, Waseda University, Okubo, Shinjuku-ku, Tokyo, Japan
‡ Department of Physics, School of Physical Sciences, Shahjalal University of Science and Technology, Sylhet, Bangladesh
§ ATP Synthesis Regulation Project, ICORP, Japan Science and Technology Agency (JST), Aomi, Koto-ku, Tokyo 135-0064, Japan
Department of Molecular Bioscience, Kyoto Sangyo University, Kamigamo, Kyoto, Japan


Shou Furuikefs present address is Faculty of Physics, Osaka Medical College, Takatsuki City, Osaka, Japan.
Katsuyuki Shiroguchifs present address is Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA.
Kengo Adachifs present address is Department of Physics, Gakushuin University, Mejiro, Toshima-ku, Tokyo, Japan.

*Corresponding author
◊Ayako Kohori and Ryohei Chiwata contributed equally to this work.