topic 10_rivier_252 - MCB 252 Cell Biology Topic 10...

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MCB 252 Cell Biology Topic 10 Microtubule Motors Reading: Lodish 18.4
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Kinesin- and dynein-mediated transport Lodish, Fig. 18- 27 Kinesins = plus end directed motors Dyneins = minus end directed motors
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MT-based motility Axonal transport: Newly synthesized proteins must be moved from cell body to tip of axon (anterograde). Old membranes must be transported back (retrograde) remember: axons can be up to 1 meter long Lodish, Fig. 18-5
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Experimental demonstration of axonal transport (pulse- chase) Lodish, Fig. 18-17 Different materials move at different speeds fast: 0.5-2.5 µm/sec slow: 10-100 nm/sec So, round-trip from spinal cord to foot, takes 3 weeks to 3 months
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Visualizing axonal transport Squid ( Loligo ) Prof. George Langford, Dartmouth Univ. dissect giant axon Alberts, Panel 11-3 microscopy Dr. Ron Vale, UCSF Movie T10M1 07_DissAxo.avi
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Bidirectional movement on MTs Lodish, Fig. 18-18
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Vesicles + ATP + MTs: no movement Above + squid cytoplasm extract: movement Substitute non-hydrolyzable ATP analog: no movement; vesicles bind tightly to MTs So, incubate MTs, cell extract, ATP analog; this should result in tight binding of motor to MTs. Collect MTs, release bound protein with ATP Identified kinesin Purification of anterograde motor
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In vitro motility assay with purified kinesin Dr. Ron Vale, UCSF 1. Adsorb purified kinesin to glass slide 2. Add rhodamine MTs + ATP 3. Visualize T10M2 Movie 07_mov-invitmtglid.avi Sliding filament assay
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Kinesin structure Lodish, Fig. 18-19 2 heavy chains; 2 light chains Head binds ATP and MTs Central stalk (coiled coil) Tail binds cargos Plus end- directed motors Linker region also called the neck
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Myosin and Kinesin Heads Kinesin linker region = “neck”
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Myosin and Kinesin Heads Myosin and Kinesin heads have related structures
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Kinesin Family Conventional (N-terminal head), Unconventional (head elsewhere)
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Model of kinesin-directed vesicle transport Lodish, Fig. 18-20
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Kinesin Movement Kinesin = 8 nm steps = one dimer/step Kinesin walks along one protofilament
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This note was uploaded on 01/29/2012 for the course MCB 252 taught by Professor Wuebbles during the Spring '08 term at University of Illinois, Urbana Champaign.

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topic 10_rivier_252 - MCB 252 Cell Biology Topic 10...

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