F₁F_o-ATP synthase is a twin rotary engine that reversibly couples ion translocation across the membrane via mechanical rotation to the formation of ATP from ADP and inorganic phosphate. The bidirectional operation mode of the F₁F_o-ATP synthase requires regulation to control the direction of rotation and its velocity. A unique feature of F₁F_o-ATP synthases from alkaliphilic bacilli is a built-in latency of ATP hydrolysis activity. This inhibition of ATPase activity is most pronounced in the ATP synthase from the thermoalkaliphile Bacillus sp. TA2.A1 (TA2F₁F_o) and is proposed to be a necessity for the survival of the organism at alkaline pH and high temperature.
In this communication we present the X-ray structure of TA2F₁ at 3.1-Å resolution. The data show that the asymmetrical γ stalk of the rotor is distorted within the cavity of the α₃β₃ cylinder, thereby preventing rotation in the ATP hydrolysis direction. A similar distortion of the γ stalk is seen in electron micrographs of the native TA2F₁F_o-ATP synthase complex indicating that this is not an artifact of the isolated TA2F₁ subcomplex.

This work was carried out in the group of Prof. Achim Stocker.

References:

• A. Stocker, S. Keis, J. Vonck, G. M. Cook, P. Dimroth;
  "The Structural Basis for Unidirectional Rotation of Thermoalkaliphilic F₁-ATPase"
  Structure, 15, 904-914, (2007); doi:10.1016/j.str.2007.06.009.