3. Microtubules Flashcards
what are microtubules composed of
alpha and beta Tubulin heterodimers
what do Tubulin dimers bind
GTP
what does:
- alpha Tubulin do to GTP
- beta Tubulin do to GTP
alpha = maintains, NEVER hydrolysed or exchanged beta = hydrolyses into GDP
what is the effect of taxol on beta tubulin
prevents disassembly of mitotic spindle following cell division ->
prevents cancer cells from dividing
when does GDP get exchanged for GTP in beta tubulin
once the subunit disassembles
microtubules are polarised, which end is the:
- end
+ end
- end = alpha tubule
+ end = beta tubule
give an example of where microtubules are found in doublets
cilia, flagella
give an example of where microtubules are found in triplets
centrioles
what is the term for inter-doublet connections
nexin linkages
what is the purpose of microtubule organising centres (MTOCs)
nucleate and organise microtubules
which end of a microtubule is associated to a MTOC
- end
give an example of a MTOC
centrosome, spindle poles
what nucleates most microtubules
gamma-tubulin ring complex
where are gamma-tubulin ring complexes found
in the pericentriolar material of a MTOC
when must dimer formation occur
before the growth of the microtubule
describe critical concentration in the dimers
the + end has lower critical concentration, this allows growth at the + end
what is dynamic instability
when microtubule ends have beta tubulin bound to GDP, the microtubule is unstable and quickly disassembles
this continues until a GTP cap is formed
what is the role of microtubule associated proteins (MAPs)
bind to, stabilise and promote assembly
describe tau in alzheimers
fragile and unfolded nature making it liable to structural abnomralities
in alzheimers, tau forms aggregates clumping together impairing cognitive function
describe the role of EB1
end binding 1 is a (+)end tracking protein that stimulates rescue and regrowth of microtubules
describe the role of kinesin 13
facilitates disassembly by hydrolysing ATP
describe the role of stathmin
binds to curves protofilaments and enhances disassembly.
why do cells modify their dynamic instability
so they can become more dynamic as cells enter mitosis
microtubules are composed of how many laterally associated protofilaments
13
