Elastic deformations of the rotary double motor of single FoF1-ATP synthases detected in real time by Förster resonance energy transfer

► FOF1-ATP synthase comprises two rotary motors with different step sizes. ► Coupling of the motors requires reversible elastic deformations. ► Single-molecule FRET is used to measure the elastic angular twist. ► Up to 108° twisting between c- and ε-subunits is found. ► Twisting is suppressed by DCCD during ATP synthesis and ATP hydrolysis.