Lecture 9 - microtubules and actin filaments Flashcards
what are microtubule subunits
tubulin heterodimers
theyre made up of one alpha and one beta tubulin
diff between plus and minus ends in MT
plus = grow fast
also shrink at this end
minus = very little if any movement
what element necassary to form micotubules in a test tube
Mg2+
why cant tubulin polymerise spontaneously
too little concentration
what is used to speed up tubulin polymerisation
gamma-tubulin and other proteins
process is called nucleation
it gives it a surface to attach to and polymerise from there
in basal bodies what do MT form
bundles of MT form in the cillia
what are MT embedded in
centrosome
what is dynhamic instability
MT switch between growing and shrinking, and this happens independently of other MT
are MT GTPase or ATPases
GTPase
which form of tubulin can polymerise
GTP tubulin
and remember GTP hydrolysis to GDP is slow
why will MT start to shrink if GTP cap is gone
GTP tubulin bind tighter to each other than GDP, so structure is less stable without the cap
starts to unravel and shrink
which protein marks GROWING microtubules and how
EB1
binds inly to GTP bound tubulin
what is catastophe
when GTP cap is lost
then MT will depolymerise
whats it called when GTP cap reforms and MT starts regrowing
rescue !
what natural thing stabilises MT
microtubule asssociated proteins
MAPs
what are the 2 neuronal MAPs
Tau
MAP2
what synthetic drug is used to stabilise MT
taxol
what ‘captures’ MT plus ends to stabilise them
microtubule capping protein
2 ways to depolymerise MT experimentally
putting cells on ice
or
drugs that prevent new assembly
another name for actin filaments
microfilaments
examples of contractile bundles that actin is found in
stress fibres
contractile rings
(and muscle too predominantly)
3 examples of non-contractle bundle that actin is found in
microvilli
lamellipodium
filopodia
what is actin filaments assembled from and whta kind of structure is it
actin monomers
thin, helical, less complex that MT
is actin ATPase or GTPase
ATPase
what form of actin will grow the filament
actin bound with ATP
what does minus end do in actin
where depolymerisation/shrinkage happens
what binds to minus end to prevent depolym in actin
capping proteins
what natural molecule stabilises actin filaments, causing the organism that produces this to be poisonous
phalloidin
means actin cant grow
2 natural molecules that precent acting polymerisation that are produced by fungus/sponge
Cytochalasin
Latrunculin
what protein binds to actin monomers and prevents it polymerising
thymosin
what do nucelating proteins do
promote polymerisation
in actin AND microtubules
what 2 proteins alter actin filament lenth/dynamics
severing protein - cuts it off, depolymerises
capping protein - stops it growin
2 proteins that change how actin filaments are organised
cross-linking proteins
bundling protein
2 prtoeins that control movement along the actin filaments
motor protein
side-binding protein
