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Kinesin and Microtubules

Kinesin and Microtubules. Molecular Motors. http://www.komsta.net/chemwalls/kinesin1-1280.jpg. http://www.itg.uiuc.edu/exhibits/gallery/pages/image-22.htm. http://mcb.berkeley.edu/labs/cande/motors.html. Microtubule Structure and Formation. Polymer of two small dimers

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Kinesin and Microtubules

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  1. Kinesin and Microtubules Molecular Motors http://www.komsta.net/chemwalls/kinesin1-1280.jpg

  2. http://www.itg.uiuc.edu/exhibits/gallery/pages/image-22.htm

  3. http://mcb.berkeley.edu/labs/cande/motors.html

  4. Microtubule Structure and Formation • Polymer of two small dimers • Alternating pattern of α- and β-tubulin • Alternation plays important role in Kinesin movement http://upload.wikimedia.org/wikipedia/commons/8/80/Microtuble.jpg http://www.daviddarling.info/encyclopedia/M/microtubule.html

  5. Microtubule Structure and Formation • Polymer structure allows for rapid assembly and disassembly • Tubulin can diffuse rapidly throughout the cell • Smaller tubulin can move more quickly than larger microtubules http://en.wikipedia.org/wiki/Image:Tubulin.jpg

  6. Unique bonding structure Resistant to thermal breakage along the strand Dynamic ends that grow and recess rapidly Leads to Dynamic Instability Tubulin will not organize (nucleate) on their own Require a pre-existing microtubule or a catalyzing protein The cell takes advantage of this and can specify where the microtubules go Microtubules

  7. Microtubules • This graph of an experiment on tubulin show the initial lag phase of three to five minutes where the tubulin are nucleating into the microtubule bases http://intl.jcb.org/cgi/reprint/101/3/755

  8. Dynamic Instability GTP-Tubulin GDP-Tubulin Hydrolysis GTP-Tubulin Cap

  9. Dynamic Instability GTP-Tubulin GDP-Tubulin Hydrolysis goes faster than tubulin addition

  10. Dynamic Instability GTP-Tubulin GDP-Tubulin New GTP Cap

  11. Kinesin • Kinesin has two ends • One end is the “tail end” which attaches to whatever is being transported such as a vesicle or organelle • The other end has two “heads” which attaches to a microtubule. These two heads walk in a “hand over hand” fashion along the microtubule http://en.wikipedia.org/wiki/Kinesin

  12. “Hand-Over-Hand Movement” • First head attaches, ADP is changed to ATP • ATP causes the linking region to straighten, placing the second head in front • Second head attaches to microtubule • ATP in the first head is hydrolyzed into ADP and phosphate, head loses rigidity and detaches • ATP is formed in the second head, moving the first head in front once again

  13. http://valelab.ucsf.edu/images/mov-procmotconvkinrev5.mov • Each step is 8 nanometers and the Kinesin travels .02-2 micrometers/second http://www.fli-leibniz.de/~kboehm/Kinesin.html

  14. http://www7.nationalacademies.org/bpa/reports_bmm-11.gif

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