The rotor tip inside a bearing of a thermophilic F 1-ATPase is dispensable for torque generation

Mohammad Delawar Hossain, Shou Furuike, Yasushi Maki, Kengo Adachi, M. Yusuf Ali, Mominul Huq, Hiroyasu Itoh, Masasuke Yoshida, Kazuhiko Kinosita

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    F 1-ATPase is an ATP-driven rotary molecular motor in which the central γ-subunit rotates inside a stator cylinder made of α 3β 3 subunits. To elucidate the role of rotor-stator interactions in torque generation, we truncated the γ-subunit at its carboxyl terminus, which forms an a helix that penetrates deeply into the stator cylinder. We used an α 3β 3γ subcomplex of F 1-ATPase derived from thermophilic Bacillus PS3 and expressed it in Escherichia coli. We could obtain purified subcomplexes in which 14, 17, or 21 amino-acid residues were deleted. The rotary characteristics of the truncated mutants, monitored by attaching a duplex of 0.49-μm beads to the γ-subunit, did not differ greatly from those of the wild-type over the ATP concentrations of 20 nM-2 mM, the most conspicuous effect being ∼50% reduction in torque and ∼70% reduction in the rate of ATP binding upon deletion of 21 residues. The ATP hydrolysis activity estimated in bulk samples was more seriously affected. The 21-deletion mutant, in particular, was >10-fold less active, but this is likely due to instability of this subcomplex. For torque generation, though not for rapid catalysis, most of the rotor-stator contacts on the deeper half of the penetrating portion of the γ-subunit are dispensable.

    Original languageEnglish
    Pages (from-to)4195-4203
    Number of pages9
    JournalBiophysical Journal
    Issue number11
    Publication statusPublished - 2006 Jun

    ASJC Scopus subject areas

    • Biophysics

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    Hossain, M. D., Furuike, S., Maki, Y., Adachi, K., Ali, M. Y., Huq, M., Itoh, H., Yoshida, M., & Kinosita, K. (2006). The rotor tip inside a bearing of a thermophilic F 1-ATPase is dispensable for torque generation. Biophysical Journal, 90(11), 4195-4203.