Effect of ε subunit on the rotation of thermophilic Bacillus F1-ATPase

F-1-ATPase is an ATP-driven motor in which gamma epsilon rotates in the alpha(3)beta(3)-cylinder. It is attenuated by MgADP inhibition and by the e subunit in an inhibitory form. The non-inhibitory form of e subunit of thermophilic Bacillus PS3 F-1-ATPase is stabilized by ATP-binding with micromolar K-d at 25 degrees C. Here, we show that at [ATP] > 2 mu M, epsilon does not affect rotation of PS3 F-1-ATPase but, at 200 nM ATP, epsilon prolongs the pause of rotation caused by MgADP inhibition while the frequency of the pause is unchanged. It appears that epsilon undergoes reversible transition to the inhibitory form at [ATP] below K-d. (C) 2009 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.