Temperature dependence of the rotation and hydrolysis activities of F 1-ATPase

Shou Furuike, Kengo Adachi, Naoyoshi Sakaki, Rieko Shimo-Kon, Hiroyasu Itoh, Eiro Muneyuki, Masasuke Yoshida, Kazuhiko Kinosita

    研究成果: Article

    28 被引用数 (Scopus)

    抄録

    F1-ATPase, a water-soluble portion of the enzyme ATP synthase, is a rotary molecular motor driven by ATP hydrolysis. To learn how the kinetics of rotation are regulated, we have investigated the rotational characteristics of a thermophilic F1-ATPase over the temperature range 4-50°C by attaching a polystyrene bead (or bead duplex) to the rotor subunit and observing its rotation under a microscope. The apparent rate of ATP binding estimated at low ATP concentrations increased from 1.2 × 106 M-1 s-1 at 4°C to 4.3 × 107 M-1 s -1 at 40°C, whereas the torque estimated at 2 mM ATP remained around 40 pN·nm over 4-50°C. The rotation was stepwise at 4°C, even at the saturating ATP concentration of 2 mM, indicating the presence of a hitherto unresolved rate-limiting reaction that occurs at ATP-waiting angles. We also measured the ATP hydrolysis activity in bulk solution at 4-65°C. F1-ATPase tends to be inactivated by binding ADP tightly. Both the inactivation and reactivation rates were found to rise sharply with temperature, and above 30°C, equilibrium between the active and inactive forms was reached within 2 s, the majority being inactive. Rapid inactivation at high temperatures is consistent with the physiological role of this enzyme, ATP synthesis, in the thermophile.

    本文言語English
    ページ(範囲)761-770
    ページ数10
    ジャーナルBiophysical Journal
    95
    2
    DOI
    出版ステータスPublished - 2008 7 15

    ASJC Scopus subject areas

    • Biophysics

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