Redox regulation of the rotation of F(1)-ATP synthase.

In F(1)-ATPase, the smallest known motor enzyme, unidirectional rotation of the central axis subunit gamma is coupled to ATP hydrolysis. In the present study, we report the redox switching of the rotation of this enzyme. For this purpose, the switch region from the gamma subunit of the redox-sensitive chloroplast F(1)-ATPase was introduced into the bacterial F(1)-ATPase. The ATPase activity of the obtained complex was increased up to 3-fold upon reduction (Bald, D., Noji, H., Stumpp, M. T., Yoshida, M. & Hisabori, T. (2000) J. Biol. Chem. 275, 12757-12762). Here, we successfully observed the modulation of rotation of gamma in this chimeric complex by changes in the redox conditions. In addition we revealed that the suppressed enzymatic activity of the oxidized F(1)-ATPase complex was characterized by more frequent long pauses in the rotation of the gamma subunit. These findings obtained by the single molecule analysis therefore provide new insights into the mechanisms of enzyme regulation.