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Summary of cytoskeleton


Department
Biological Sciences
Course Code
BIOB10H3
Professor
Rene Harrison

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StructureDescription Function Monomer/Compone
ntEndsPolymerization
Microtubules
(cytoskeleton)
- can see 3 from x-ray
crystallography
- Diseases: Alzheimers
(tau defect),
neurogenerative dieases
(motor defects),
flagella/cilia defects,
taxol (chemotherapy
agent)
- cilia (respiratory
epithelium), flagella
(sperm)
- polar (each end
structurally a little
different)
- half life: 10min
- rapidly turnover
(unstable)
- stability can be
increased by binding
MAPS (MT-
associated proteins;
MAP2, tau) to walls
of MTs to prevent
MTs from
depolymerizing
- stable MTs used to
transport
organelles/vesicles
(highways)
- cell
structure/keeps
organelles in place
- flagella/cilia
beating
- mitotic spindle
formation
- composed of
tubulin
heterodimers (each
with - and -
subunits &
polymerize to make
MTs)
- (-)-charged is
embedded in
centrosome (MT-
organizing centre:
MTOC where
polymerization begins
[with -tubulin which
is structurally
different from - and
-)
- (+)-charged extends
toward plasma
membrane
- -tubulin binds to
GTP to allow
polymerization
- GTPGDP slowly
after incorporation
into MT wall
- polymerize/
depolymerize at (+)-
charged
enddynamic
instability
- polymerize into a
protofilament
(arrange around a
hollow core: forms
the MT)
Microtubule Motors- multiprotein
complexes
- 2 domains: MT-
binding domain &
cargo binding
domain
- move according to
polarity of MTs
-ATPases
- move
vesicle/organelles
cargo along MTs
- dynesin moves to
(-) end (retrograde)
- kinesin moves to
(+) end (anterograde)
Dynesin
(Microtubule Motor) - MT-binding domain
- 2 heavy chains (polypeptides)globular head
- several light chains: bind to dynactin (protein that
mediates binding to cargo)binds to cargo
- site of ATP
hydrolysis
- moves to (-) end
(retrograde)
- moves several nm
per ATP hydrolyzed
- holds Golgi in place
- moves endosomes, phagosomes,
lysosomes to interior of cell
- moves chromosomes to the (-)
end of poles during mitosis
Kinesin
(Microtubule Motor) - MT-binding domain / cargo binding domain
- 2 heavy chains
- 2 light chains: bind to kinectin (kinesin receptor on
- moves to (+) end
(anterograde)- moves secretory vesicles,
peroxisomes, mitochondria
towards plasma membrane
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vesicles)
Mitotic Spindle
(MT)- formed when MT cytoskeleton disassembles & reforms
during cell division (during which, dynesin moves
chromosomes to (-) end)
- (-) end in spindle
poles
- (+) end attach to
chromosome
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