Berlin 2005 – wissenschaftliches Programm
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AKB: Biologische Physik
AKB 25: Active Networks and Cell Motility
AKB 25.5: Vortrag
Freitag, 4. März 2005, 16:30–16:45, TU H2013
The Bipolar Mitotic Kinesin Eg5 Moves on Two Microtubules — •Lukas C. Kapitein1, Erwin J.G. Peterman1, Benjamin H. Kwok2, Jeffrey H. Kim2, Tarun M. Kapoor2, and Christoph F. Schmidt1 — 1Dept. Physics, Vrije Universiteit, Amsterdam, NL — 2Lab. Chem. Cell Biol., The Rockefeller University, New York, NY, USA
During cell division mitotic spindles dynamically self-assemble with the help of microtubule-based motor proteins. The bipolar organization of spindles is essential for proper segregation of DNA and in eukaryotes requires BimC motor proteins, a family of homotetrameric kinesins. Hypotheses for bipolar spindle formation include the No-dqpush-pull mitotic muscleNo-dq model in which BimC and opposing motor proteins act between overlapping microtubules. The mitotic spindle is, however, very different from skeletal muscle in that it is a very dynamic structure which turns over its components within minutes while maintaining its shape and exerting forces. We have shown using in vitro assays with single-molecule fluorescence microscopy and optical tweezers that the BimC kinesin Eg5 drives sliding of microtubules dependent on their relative orientation at speeds comparable to spindle pole separation rates. Additionally, we found that Eg5 can tether microtubule plus-ends, suggesting an additional microtubule-binding mode for Eg5. Based on these data we suggest a physical model in which BimC kinesins contribute to mitotic spindle assembly by aligning and pushing apart microtubules.