7 – Microtubules I Flashcards
Microtubules - what is it amde of & shape
αβ-tubulin dimer
cylinders
Microtubules Provide
structure to cells & enable long-range transport
microtubules found in
all eukaryotes
microtubules Organized by
centrosome in animal cells – polar structure
Adjacent to nucleus
(-) end in centrosome/(+) end extend out onto cell periphery
microtubules are continuously…
built/broken down/rebuilt
microtubules are roadways for…
roadways for intracellular transport
microtubules are… of neurons
backbones
Microtubules in neurons = densely packed
Some ends(dendrites) have mixed polarity with (-) ends
(+) ends point out
Specialized microtubule-based structures
cilia of trachea
Special form of flagella
Flagella –tails used for swimming = also cilia
microtubules are built from…
Built from tubulin heterodimers – always immediately put into dimer structure
-alpha beta tubulin
what drives polymerization process?
GDP in beta tubulin
Tubulin
First identified as target of drug colchicine
-cochicine binding drug
Rate constant of microtubule polymerization is …
why?
Less clear
-higher critical concentration on plus end
lower critical concentration on minus end
Because 13 different places where tubulin can bind to microtubule
Microtubule end = made of
GTP-tubulin & maybe sheet-structures
have elongated protofilaments
while microtubule is growing, … is added
what does it do
GTP tubulin
the GTP tubulin at the end of the polymer is protecting and protecting its entire structure
Loss of GTP-cap = result in
what is the GTP cap
switch from growth to rapid shrinkage
GTP cap = GTP-β-tubulin
CATASTROPHE - RESCUE
GTP state
GDP state
which one is likely to form/disassemble polymer?
GDP state = disassemble
GTP state = assembly
Tubulin can be … OR….
(shape)
straight OR curved
Quick restructure of microtubules from
dynamic instability
Rapid switching of polymer from stable to unstable form
Dynamic instability = first deduced & later observed
explain the research
Regaining the GTP Cap After the Needle Breaks the Microtubule:
When a microtubule is severed, the new plus-end can either catastrophe (rapid depolymerization) or rescue(repolymerization). The rescue process depends on whether free GTP-tubulin dimers are available to add to the plus-end. If the tubulin concentration is high enough, polymerization resumes, and the microtubule can regain its GTP-cap, stabilizing growth.
microtubules are target of broad class of …
chemotherapy drugs
-Taxol stabilizes microtubules
DZ-2384 = synthetic derivative of natural product from marine sponge
