Scenario 2

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Scenario 2
Scenario 2 Fast transport of vesicles
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Scenario 2

• Fast axonal flow
• Organelles such as mitochondria and precursors of
  synaptic vesicles
• Transported from near centrosome in cell body to
  axon ending
• Movements observable with light microscope, using
  phase contrast or interference contrast

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Scenario 2

• Discovery of the motor protein kinesin
• Transport inhibited by AMPPNP (non-hydrolyzable
  analogue of ATP
• In AMPPNP, organelles are arrested attached to
  microtubules cf rigor
• Microtubules purified from brain in presence
  AMPPNP have ATP-ase activity

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Scenario 2

• Discovery of the motor protein kinesin
• Microtubules purified from brain in presence
  AMPPNP have ATP-ase activity
• Assay purified motor protein by observing mt
  gliding in vitro

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Scenario 2

• Motor characteristics of kinesin I
• Dilution of kinesin shows a single molecule
  moves mt as fast as any greater number
• Can study force exerted by single molecules
• Kinesin moves in 8 nm steps ( 1 heterodimer)
  towards mt plus end i.e. Anterograde transport
• Movement through many cycles without detachment
  is named processive

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Scenario 2

• Motor characteristics of kinesin I
• Dilution of kinesin shows a single molecule
  moves mt as fast as any greater number
• Can study force exerted by single molecules
• Kinesin moves in 8 nm steps ( 1 heterodimer)
  towards mt plus end i.e. Anterograde transport
• Movement through many cycles without detachment
  is named processive

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Scenario 2

• Linkage of kinesins to cargo vesicles
• Drosophila gene Sunday Driver has phenotype
• similar to kinesin mutants, homologues in worm
• mouse and human.
• Amyloid Precursor Protein (APP), important in
  Alzheimers disease, may be a kinesin cargo
  receptor
• Kinesin transport regulated by phosphorylation
  of (kinesin) light chains - abnormal in
  neurodegenerative diseases?

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Scenario 2
Scenario 2 Fast transport of vesicles
End
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Introduction
Microtubules Microfilaments Intermediate
filaments

Cytoskeleton

Kinesin Dynein Myosin
Motor proteins
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