Dresden 2009 – scientific programme
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BP: Fachverband Biologische Physik
BP 12: Single Molecules
BP 12.3: Talk
Wednesday, March 25, 2009, 10:30–10:45, HÜL 186
Single-molecule measurement of protein friction between kinesin and the microtubule surface and its relation to lattice diffusion — 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
Friction within an engine or between a vehicle and its track plays a crucial role in the operation of macroscopic machines. Biological machines such as muscle are also subject to frictional forces. The concept of protein friction has been used in theoretical studies, but experimental studies are scarce. We have developed techniques based on optical tweezers to measure the friction between individual kinesin-8 molecules and microtubules in the presence of ADP. At low speeds we find a friction coefficient of 700±300 nNs/m, which is in good agreement with the diffusion coefficient measured under identical conditions. This confirms the fundamental connection between friction and diffusion. We measured a non-linear dependence of friction on velocity, allowing us to estimate the distance between diffusional hopping steps of 8.0±0.6 nm. This step size was confirmed by direct resolution of step-wise motions as well as a fluctuation analysis; thus kinesin-8 steps between adjacent tubulin dimers. Our experiments therefore confirm the presence of protein friction—an important parameter for active protein locomotion limiting the efficiency.