Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 26: Posters II

BP 26.23: Poster

Thursday, February 28, 2008, 17:00–19:30, Poster A

Searching the proper Model for F₁-ATPase rotation — •Florian Werz¹, Alexander Kovalev¹, Nawid Zarrabi¹, Carsten Tietz¹, Michael Börsch¹, Dirk Bald², and Jörg Wrachtrup¹ — ¹3. Physikalisches Institut, Universität Stuttgart, Germany — ²Department of Structural Biology, Vrije Universiteit Amsterdam, Netherlands

The F-type ATP-Synthase is a composed rotary motor enzyme in the plasmamembrane of prokaryotes and in the inner membrane of mitochondria of eukaryotes, respectively, producing the universal fuel ATP, which is used to sustain nearly every chemical reaction in cells. The F₁-part of the enzyme can work in reverse hydrolyzing ATP and rotating backwards showing 120^∘ steps resulting from the threefold symmetry of its α₃β₃-stator-complex. We recorded trajectories up to half an hour with high time resolution (down to Δ = 1ms) of Polystyrol beads attached to the rotating γ-subunit of single F₁-ATPase using wide field microscopy. We recorded the same molecule for different concentrations of ATP and ADP and therefore different rotational speeds. Analyzing data by hidden Markov models (HMM) we found to reproduce dwell time histograms a model with three or more consecutive states per visible state was required. Introduction of an additional state corresponding to the ADP-inhibited state, which stops rotation of F₁-ATPase for relative long times (up to minutes), significantly improved the fit.