Dresden 2009 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 15: Motor Proteins
BP 15.1: Vortrag
Mittwoch, 25. März 2009, 14:30–14:45, ZEU 260
Diffusion of yeast kinesin-8 on the microtubule lattice is a random walk with 8-nm steps — •Volker Bormuth1, Vladimir Varga1, Jonathon Howard1, and Erik Schäffer2 — 1MPI of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany — 2Biotechnology Center, TU Dresden, Tatzberg 47-51, 01307 Dresden, Germany
The yeast kinesin-8 (Kip3p) walks highly processive towards the plus-end of microtubules in the presence of ATP. In contrast, we found that in the presence of ADP Kip3p diffuses in a one-dimensional manner on the microtubule lattice. Using single molecule fluorescence we measured that the diffusion coefficient was 5400±1500 nm2/s with an average lifetime on the microtubule lattice of 8 s. The diffusion did not require the highly charged C-termini of tubulin, unlike kinesin-13. We biased the diffusion using optical tweezers and analyzed the time-traces of biased diffusion by means of a fluctuation analysis. We found that Kip3p diffusion is a multi-step process with a physical step size of 8 nm and an average dwell time of 6 ms per step. The step size was supported by the direct observation of 8 nm motions and a non-linear force-velocity relationship. At high forces the biased diffusion appeared like a one-step process indicating the presence of only one force-dependent step. Our results compared well with Monte Carlo simulations and suggest that Kip3p diffusion is a undirected, hand-over-hand, random walk along the microtubule lattice.