kinesin and microtubules molecular motors
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Kinesin and MicrotubulesKinesin and Microtubules
Molecular MotorsMolecular 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 Microtubule Structure and FormationStructure and Formation
Polymer of two small Polymer of two small dimersdimers
Alternating pattern of Alternating pattern of αα- and - and ββ-tubulin-tubulin
Alternation plays Alternation plays important role in important role in Kinesin movementKinesin movement
http://www.daviddarling.info/encyclopedia/M/microtubule.html
http://upload.wikimedia.org/wikipedia/commons/8/80/Microtuble.jpg
Microtubule Microtubule Structure and FormationStructure and Formation
Polymer structure Polymer structure allows for rapid allows for rapid assembly and assembly and disassemblydisassembly
Tubulin can diffuse Tubulin can diffuse rapidly throughout the rapidly throughout the cellcell Smaller tubulin can Smaller tubulin can
move more quickly move more quickly than larger than larger microtubulesmicrotubuleshttp://en.wikipedia.org/wiki/Image:Tubulin.jpg
MicrotubulesMicrotubules
Unique bonding Unique bonding structurestructure Resistant to thermal Resistant to thermal
breakage along the breakage along the strandstrand
Dynamic ends that Dynamic ends that grow and recess grow and recess rapidlyrapidly
Leads to Dynamic Leads to Dynamic InstabilityInstability
Tubulin will not Tubulin will not organize (nucleate) organize (nucleate) on their ownon their own
Require a pre-existing Require a pre-existing microtubule or a microtubule or a catalyzing proteincatalyzing protein The cell takes The cell takes
advantage of this and advantage of this and can specify where the can specify where the microtubules gomicrotubules go
MicrotubulesMicrotubules
This graph of an This graph of an experiment on tubulin experiment on tubulin show the initial lag show the initial lag phase of three to five phase of three to five minutes where the minutes where the tubulin are nucleating tubulin are nucleating into the microtubule into the microtubule basesbases
http://intl.jcb.org/cgi/reprint/101/3/755
Dynamic InstabilityDynamic Instability
GTP-Tubulin Cap
GTP-Tubulin
GDP-Tubulin
Hydrolysis
Dynamic InstabilityDynamic Instability
Hydrolysis goes faster than tubulin addition
GTP-Tubulin
GDP-Tubulin
Dynamic InstabilityDynamic InstabilityGTP-Tubulin
GDP-Tubulin
New GTP Cap
KinesinKinesin
Kinesin has two endsKinesin has two ends One end is the “tail end” One end is the “tail end”
which attaches to whatever which attaches to whatever is being transported such is being transported such as a vesicle or organelle as a vesicle or organelle
The other end has two The other end has two “heads” which attaches to a “heads” which attaches to a microtubule. These two microtubule. These two heads walk in a “hand over heads walk in a “hand over hand” fashion along the hand” fashion along the microtubulemicrotubule
http://en.wikipedia.org/wiki/Kinesin
““Hand-Over-Hand Movement”Hand-Over-Hand Movement”
First head attaches, ADP is changed to ATP First head attaches, ADP is changed to ATP ATP causes the linking region to straighten, ATP causes the linking region to straighten,
placing the second head in frontplacing the second head in front Second head attaches to microtubuleSecond head attaches to microtubule ATP in the first head is hydrolyzed into ADP ATP in the first head is hydrolyzed into ADP
and phosphate, head loses rigidity and and phosphate, head loses rigidity and detaches detaches
ATP is formed in the second head, moving ATP is formed in the second head, moving the first head in front once againthe first head in front once again
http://valelab.ucsf.edu/images/mov-procmotconvhttp://valelab.ucsf.edu/images/mov-procmotconvkinrev5.movkinrev5.mov
Each step is 8 nanometers and the Kinesin Each step is 8 nanometers and the Kinesin travels .02-2 micrometers/secondtravels .02-2 micrometers/second
http://www.fli-leibniz.de/~kboehm/Kinesin.html
http://www7.nationalacademies.org/bpa/reports_bmm-11.gif
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