Cell Signalling 2

Question 1

When are G proteins inactive?

Answer 1

When bound to GDP

Question 2

When are G proteins active?

Answer 2

When bound to GTP

Question 3

What 2 forms do G proteins exist in ?

Answer 3

1. Within trimeric complex
2. As a single monomeric protein

Question 4

How many members of monomeric G protein superfamily are there ?

Answer 4

Over 150

Question 5

What are the catalysts required for G protein activation/inactivation ?

Answer 5

1. Guanine nucleotide exchange factor (GEFs) to aid GDP/GTP exchange
2. GTPase accelerating protein (GAPs) to aid in GTP hydrolysis

Question 6

What is Ras for ?

Answer 6

Cell division and growth

Question 7

What is rab for ?

Answer 7

Membrane transport and vesicular transport

Question 8

What are rac and rho for ?

Answer 8

Cytoskeleton organisation and migration

Question 9

What is phosphorylation?

Answer 9

A way to active proteins.
A phosphate is added to specific amino acids on target proteins from ATP.

Question 10

What amino acids can receive phosphate groups ?

Answer 10

1. Tyrosine
2. Serine
3. Threonine

Question 11

What reverses phosphorylation?

Answer 11

Protein phosphatase

Question 12

How is cAMP produced ?

Answer 12

From ATP by the enzyme adenylyl cyclase

Question 13

Describe the structure of adenylyl cyclase

Answer 13

It consists of two transmembrane domains, joined by a catalytic intraceullar domain

Question 14

What is the adenylyl cyclase signalling pathway ?

Answer 14

Adenylyl cyclase activates cAMP which activates PKA

Question 15

How does PKA get activated ?

Answer 15

1. Inactive PKA consists of two regulatory subunits and two catalytic kinase subunits
2. cAMP binds to the regulatory subunits causing the molecule to dissociate
3. Two resulting monomeric kinase units are active and can bind and phosphorylate target proteins

Question 16

What is cAMP degraded into ?

Answer 16

A 5’ monophosphate (AMP) by a cAMP phosphodiasterase