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small GTPases Flashcards

1
Q

B tubulin is a

A

GTPase

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2
Q

alpha tubular is not a

A

GTPase

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3
Q

draw the Btubulun.GTP Btubulin.GDP exchange

A

what does it drive

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4
Q

Btubulun.GTP

A

straight filament

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5
Q

Btubulun.GDP

A

curved protofilament, due to GTP hydrolysis changing subunit conformation, weakens bonds in polymer

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6
Q

what is a GTP cap

A

adding GTP tubular at the + end which stabilises the protofilament, GDP is unstable

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7
Q

+ end

A

Btubulin bound to GTP which is more dynamic

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8
Q

loss of GTP cap =

A

release of tubular –>catastrophic shrinkage

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9
Q

most formins are activated by which GTPase

A

Rho-gtpase

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10
Q

nucleation of formins

A
  • FH1 and FH2 domains, work like swing arms, sequential working as a dimer with each FH adding an actin monomer
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11
Q

one of the FH monomers adds an actin the other is for

A

regulagulation proteins such as profilin

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12
Q

actin filaments are nucleated from

A

the plus end - straight filaments = forming

branched - arp 2/3 complex

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13
Q

thymosin and profilin

A

compete to bind G actin

  • profilin - favours ATP exchange on G actin - pro polymerisation
  • thymosin - sequesters actin away from filament - anti-polymerisation
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14
Q

how do GPRCs transduce signals

A

they use an intermediate GTPase - a large GTPase and then a small gtpase

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15
Q

examples of small GTPases actions

A
  • initiation and elongation
  • SRP/SR family
  • tubular and cytoskeleton motor
  • small monomeric GTPase - Ras superfamily and Rho,Rac and Cdc42 rho gtpase
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16
Q

GAP

A

GTPase activating protein

increases rate of GTP to GDP bound (inactivating GTPase)

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17
Q

GEF

A

GTP/GEF exchange factor - activate the exchange

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18
Q

GDI

A

GDI dissosciation inhibitor - decrease exchange of GTP for GDP

19
Q

Rho family and what do they do

A

Rho, Rac and cdc42

relay signals from surface receptors to cytoskeleton and elsewhere

20
Q

central regulator of cell polarity

21
Q

once activates small GTPase activates target via

A 
molecular switches - or directly 
small GTPase(2) or through a kinase
22
Q

localised Cdc42 activation by siganl

A

recruitment effectors…

  • microtubule cytoskeleton
  • actin cytoskeleton
  • membrane trafficking
  • cell contacts
23
Q

cdc42 in golgi orientation and polarised actin cytoskeleton

A

cdc42 - WASP - ARP2/3 - actin

24
Q

cdc42 in centrosome and polarised MTs

A

cdc42 - PAK - stathmin - MTs

25
Q

cdc42 in polarised secretion

A

cdc42 - par cplx - scribble cplx - membrane trafficking - polarised secretion

26
Q

alternative cdc42 in MTs

A

cdc42 - parcplx - GSK3/APC - Mts

27
Q

PAR proteins

A
  • responsible for asymmetric positioning of the mitotic spindle and proteins and RNAs involved in the cells fate distinctions
28
Q

mutation in PAR proteins

A

mitotic spindle and PARtitioning defective

29
Q

Anterior PAR proteins

A

required to prevent PAR proteins from localising at the anterior and visa versa - POLARISED CELL

30
Q

LBK1

A

is a PAR protein in humans

  • inactivate, cells are not polarised
  • found in the human colon
  • mutation - abnormal growth of lining in gut - polyps
31
Q

Par3 - Par 6 - aPKC complex

A

epithelial cell polarity

- top/bottom, organelle distribution, membrane lipid composition

32
Q

apical surface permeable to

A

H2O, faces the external milieu, SA can be increased

33
Q

basolateral surface

A

impermeable, faces internal milieu and blood supply

34
Q

PAR proteins with crumbs and scribble

A
  • organise cell polarity

- influence each other by phosphorylation, localisation at cell junctions and bind/position small GTPases

35
Q

tight junction localize

A

PAR + crumbs

36
Q

scribble localizes

A

basolateral junction

37
Q

Par proteins are

A

kinases which switch other proteins on/off

scaffolding factors - recruit and interact with other proteins regulating them

38
Q

cdc42 controls

A

everything

39
Q

RhoGTP - focal adhesion

A

RhoGTP - ROCK- coffin myosin - more stress fibres - focal adhesion

RhoGTP - formin - more stress fibres - focal adhesion

40
Q

RacGTP - lamellopodia

A

RacGTP - PAK - filamin myosin - less stress fibres - lamellopodia

RacGTP - WASP - Arp2/3 - branched actin - lamellopodia

41
Q

cdc42 - filopodia

A

cdc42 - WASP - Arp 2/3 - branched actin - filopodia

42
Q

cdc42 - filopodia

A

cdc42 - WASP - Arp 2/3 - branched actin - filopodia

43
Q

examples of what CDC42 controls

A

migrating fibroblast - extending leading edge
cytotoxic T cell - contact with target cell, formation strong contact
epithelial cell - apical basolateral
polarised dividing cell - c.elegans - asymmetric division

Microbiology Essay plans (9 decks)

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