Lecture 9 - microtubules and actin filaments Flashcards

1
Q

what are microtubule subunits

A

tubulin heterodimers
theyre made up of one alpha and one beta tubulin

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2
Q

diff between plus and minus ends in MT

A

plus = grow fast
also shrink at this end

minus = very little if any movement

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3
Q

what element necassary to form micotubules in a test tube

A

Mg2+

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4
Q

why cant tubulin polymerise spontaneously

A

too little concentration

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5
Q

what is used to speed up tubulin polymerisation

A

gamma-tubulin and other proteins
process is called nucleation
it gives it a surface to attach to and polymerise from there

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6
Q

in basal bodies what do MT form

A

bundles of MT form in the cillia

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7
Q

what are MT embedded in

A

centrosome

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8
Q

what is dynhamic instability

A

MT switch between growing and shrinking, and this happens independently of other MT

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9
Q

are MT GTPase or ATPases

A

GTPase

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10
Q

which form of tubulin can polymerise

A

GTP tubulin
and remember GTP hydrolysis to GDP is slow

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11
Q

why will MT start to shrink if GTP cap is gone

A

GTP tubulin bind tighter to each other than GDP, so structure is less stable without the cap
starts to unravel and shrink

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12
Q

which protein marks GROWING microtubules and how

A

EB1
binds inly to GTP bound tubulin

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13
Q

what is catastophe

A

when GTP cap is lost
then MT will depolymerise

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14
Q

whats it called when GTP cap reforms and MT starts regrowing

A

rescue !

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15
Q

what natural thing stabilises MT

A

microtubule asssociated proteins
MAPs

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16
Q

what are the 2 neuronal MAPs

17
Q

what synthetic drug is used to stabilise MT

18
Q

what ‘captures’ MT plus ends to stabilise them

A

microtubule capping protein

19
Q

2 ways to depolymerise MT experimentally

A

putting cells on ice
or
drugs that prevent new assembly

20
Q

another name for actin filaments

A

microfilaments

21
Q

examples of contractile bundles that actin is found in

A

stress fibres
contractile rings
(and muscle too predominantly)

22
Q

3 examples of non-contractle bundle that actin is found in

A

microvilli
lamellipodium
filopodia

23
Q

what is actin filaments assembled from and whta kind of structure is it

A

actin monomers
thin, helical, less complex that MT

24
Q

is actin ATPase or GTPase

25
what form of actin will grow the filament
actin bound with ATP
26
what does minus end do in actin
where depolymerisation/shrinkage happens
27
what binds to minus end to prevent depolym in actin
capping proteins
28
what natural molecule stabilises actin filaments, causing the organism that produces this to be poisonous
phalloidin means actin cant grow
29
2 natural molecules that precent acting polymerisation that are produced by fungus/sponge
Cytochalasin Latrunculin
30
what protein binds to actin monomers and prevents it polymerising
thymosin
31
what do nucelating proteins do
promote polymerisation in actin AND microtubules
32
what 2 proteins alter actin filament lenth/dynamics
severing protein - cuts it off, depolymerises capping protein - stops it growin
33
2 proteins that change how actin filaments are organised
cross-linking proteins bundling protein
34
2 prtoeins that control movement along the actin filaments
motor protein side-binding protein