CellSig4 - 27

Question 1

Characterise small GTPases

Answer 1

Small monomeric 21kDa proteins with intrinsic GTPase activity that can bind to and hydrolyse GTP

Question 2

What modifications do many GTPases have?

Answer 2

Lipid modifications to target them to specific membrane sites

Question 3

What family do small GTPases belong?

Answer 3

Ras

Question 4

What region of the small GTPase is most important?

Answer 4

Switch region alters the protein resulting in its activation when bound

Question 5

Outline the activation/deactivation cycle of small GTPases

Answer 5

Active (quick GTP hydrolysis) > inactive (slow removal of GDP) > inactive (quick GTP association)

Question 6

What inactivates GTPase?

Answer 6

GAP - GTPase activating protein

Question 7

What activates GTPase?

Answer 7

GEF - guanine nucleotide exchange factor

Question 8

What sequesters GDP proteins for GTPase?

Answer 8

GDI - guanine nucleotide dissociation inhibitor

Question 9

What is Arf?

Answer 9

ADP ribosylation factor - controls general aspects of membrane trafficking

Question 10

What is Rab?

Answer 10

Ras-like in brain - regulation of vesicle trafficking, docking and sorting

Question 11

What is Ran?

Answer 11

Ras-like nuclear - controls nuclear import and nuclear export

Question 12

What is Ras?

Answer 12

Ras sarcoma - master regulator of cell growth and survival

Question 13

What is Rho?

Answer 13

Ras homology - maintains cell structure and polarity

Question 14

What is imperative in regulation of Arf family proteins?

Answer 14

Localisation of GEF

Question 15

What is key to specificity of vesicle targetting?

Answer 15

GEF and GDI

Question 16

Outline the distribution of Ran across the nuclear membrane

Answer 16

Ran-GTP inside, Ran-GDP outside nucleus

Question 17

How is the Ran distribution maintained?

Answer 17

Ran-GEF in nucleus, Ran-GAP and RanBP outside

Question 18

What does RanGTP do?

Answer 18

Targets empty importins to the cytosol

Question 19

What does RanGTP do once in the cytosol?

Answer 19

Dissociates from importin, hyrdolysed to RanGDP and is imported

Question 20

What does MAP stand for?

Answer 20

Mitogen activating protein

Question 21

Outline the Ras pathway

Answer 21

Active Ras > MAP k.k.kinase (Raf) > MAP k.kinase (Mek) > MAP kinase (Erk) > internal changes

Question 22

Name 3 Rho family GTPases

Answer 22

RhoA, Rac1 and Cdc42

Question 23

What do Rho family GTPases do?

Answer 23

Coorfinate actin cytoskeletal organisation

Question 24

What does RhoA do?

Answer 24

Stabilises and consolidates actin filaments into more rigid framework known as stress fibres

Question 25

What does Rac1 do?

Answer 25

Organises new actin filaments into fynamic ruffling structures or lamellipodia

Question 26

What does Cdc42 do?

Answer 26

Polymerises actin filaments and forms actin spijes or filopodia

Question 27

What is a CRIB domain?

Answer 27

Cdc42/Rac1 Interaction/Binding domain