Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 22: Molecular Machines

BP 22.9: Talk

Thursday, March 29, 2007, 12:15–12:30, H43

Stepsize of the two rotary motors of FoF1-ATP synthase monitored by single-molecule FRET — Monika Düser, Nawid Zarrabi, Rolf Reuter, Dongmei Ji, Frank-Mario Boldt, and •Michael Börsch — 3. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart

FoF1-ATP synthases are the membrane-embedded enzymes in mitochondria, chloroplasts and bacteria which supply cells with the chemical 'energy carrier' adenosine triphosphate, ATP. The enzyme consists of two coupled counteracting rotary motors. The Fo motor is driven by the electrochemical potential difference of protons across the membrane and has 10 proton binding sites. However, the isolated F1 motor can be driven by ATP hydrolysis and rotates in 120° steps in opposite direction. We investigate the elastic energy storage within FoF1 caused by the symmetry mismatch of the two motors (10-step versus 3-step per 360° turn) using time resolved single-molecule Förster resonance energy transfer, FRET. Therefore we have introduced pairs of two fluorophores at several positions within the Escherichia coli enzyme using eGFP-fused subunits and specific amino acid labeling. To switch-on and control the ATP production of an individual FoF1-ATP synthase we recently developed local electrochemical proton generation at the tip of a nanoelectrode in the confocal detection volume. Multiparameter FRET data provide insights into the varying stepsize of the Fo motor during ATP synthesis, and into the action mode of the non-competitive inhibitor aurovertin which modulates the rotary motion during ATP hydrolysis.