Regensburg 2010 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 7: Posters: Biological Machines, Motor Proteins

BP 7.7: Poster

Montag, 22. März 2010, 17:15–20:00, Poster B1

A tetrameric Kinesin-1/Kinesin-5 chimera promotes fast relative sliding of microtubules — •Alok D. Wessel, Christina Thiede, Stefan Lakamper, Stefanie Reiter, and Christoph F. Schmidt — Drittes Physikalisches Institut, Georg-August-Universität Göttingen, Germany

The Eg5 protein from Xenopus laevis is a homo-tetrameric motor protein which moves on microtubules (MT) in a processive manner and is capable of sliding two MT apart. Single motors show a directional motility with low velocity (≈ 20 nm/s) as well as a diffusive behavior on MTs. The balance between directional and diffusive behavior is altered by cargo binding, i.e. crosslinking of MTs, or by a change of the ionic strength. In order to obtain a tetrameric model system with more clearly defined properties and motile phases, we constructed a chimera, DK4mer, by replacing Eg5-motor domain and neck-linker by the homologous regions of Kinesin-1 (D. melanogaster). Here we show that this tetramer, just like Eg5, promotes relative sliding when binding between two microtubules. DK4mer, however, slides two antiparallel MTs apart with a ∼40fold higher velocity than Eg5, between 700 and 1100 nm/s. In multi-motor relative gliding assays, different binding geometries and velocities could be observed depending on the relative MT polarity and on residual motors on the substrate surface. We further measured the dependence of relative sliding on the ionic strength. Whereas surface gliding velocity remained unchanged, the relative velocity of two MT increased by ∼400 nm/s when increasing salt concentration from 0 to 70 mM KCl in 30 mM Pipes buffer.