G protein coupled receptors

Question 1

g protein coupled receptors are — protein w MW of 35k-70k
they pass the membrane —– times
at least — different types of receptors
these include:

Answer 1

• monomeric
• 7 times
• 500
• light taste smell receptors and neurotransmitters

Question 2

key points of g-proteins:
1. an enzyme composed of — units which are:
2. binds to and hydrolysis —- to —
3. —- when GDP bound
4.—- when GTP bound
5. acquires — affinity for GTP when its associated receptor is activated

Answer 2

• 3 subunits alpha gama and beta
• GTP to GDP
• inactive
• active
• high

Question 3

1.the activity status of G protein is determined by the — subunit
2. – families of G alpha proteins based on — similarities these are:
3. the main purpose of G protein is to — amplifier or — protein activity

Answer 3

• alpha
• 4
• structural
• Gas , Gai , Gaq , Ga12
• regulate
• effector

Question 4

beta and gamma exist as — and have – enzymayic activity
- we have – different b and – different y
- they can also exert — activity

Answer 4

• dimers
• no
• 6
  -11
• signilliging

Question 5

mechanism of action of the GPCR:
1.——
- the alpha and gamma of G proteins anchor it to the membrane in an — state
- the G protein is not linked to the —
- G protein has —–
2. —–
- receptor ligand binds to —-
- the occupied receptor couples w the —-
- GDP is replaced w —
3. —–
- alpha-gtp is the — form of the receptor
- alpha-gtp complex dissociates from the receptor to interact w the —-
4. activation of —–
—- is an enzyme that generates cAMP and important 2nd messenger in cells
this enzyme can be activated by —– ( b adrenergic receptors ) and its inhibited by —-

Answer 5

-preactivation
- unbound / inactive
- receptor
- GDP -protein
- ligand binding and activation
- GPCR
- alpha subunit
- GTP
- signal generation
- active
- effector enzyme
- adenylate cyclase
- adenylate cyclase
- GPCR ( b adrenegenic receptors , G alpha s )
- alpha adrenegnic receptors
-

Question 6

— activates protein kinases

Answer 6

cAMP

Question 7

cAMP-dependetn kinases have many substrate as:
cAMP is metabolised by —–

Answer 7

• substrates include: ion channels and metabolic pathways
• phosphodiesterase ( from cAMP to AMP )

Question 8

G alpha s activares —– and is inhibited by —-

Answer 8

adenyl cyclase , G alpha i ( inhibited by pertussis toxin whopping cough )

Question 9

the GTPase activity of the alpha subunit is —- when the effector protein Is bound which causes hydrolysis of ——-
the GDP-bound alpha subunit reunites w the — complex

Answer 9

• increased
• GTP to GDP
• By complex
  ( this is how the GPCR is switched off )

Question 10

regulatory control of GPCR :
1. —- ligand bound receptor acts GEF and accelerates signalling
2. —– By acts as GDI preventing GDP release which inhibits signalling
3. —– stimulates GTPase activity and turn off signalling

Answer 10

• guanine nucelotide exchange factors ( GEF )
• guanine nucleotide dissociation inhibitor ( GDI )
• GTPase accelerating proteins ( GAPs)

Question 11

when adenylate cyclase activity is disrupted:
—- aka travellers diarrhoea
— modification of G alpha s and cant hydrolyse —- ( locked on )
- elevated cAMP levels in colonic epithelium cause —- of water and ions
- it leads to:
- treatment includes:

Answer 11

• e coli toxins
• covenant
• gtp
• efflux
• severe diarrhoea and dehydration
  1. loperamide/imodium acts as an opioid receptor agonist in large intestine
  2. treatment : opiate receptor coupled to Gi
  3. through Gi opium antagonises the out of control Gs

Question 12

activation of phopsholidser c by the GPCR signalling:
- an —– activated effector protein and classically activated by —-
—- phosphoinositide PIP from the membrane
produces second messengers:

Answer 12

• alternative g protein
• G alpha q
• hydrolysis
• DAG and inositol triphosphate IP3

Question 13

—– is soluble in water and binds to the IPS receptor in er
results in — release for smooth muscle contraction , hormone release and neurone transmitter release . the signal terminated by —- of terminal phosphate

Answer 13

• IP3
• Ca+2
• removal

Question 14

— lipid soluble and activates protein kinase c ( PKC ) in the membrane
there are at least — types of PKU and have many physiological function

Answer 14

• DAG
• 6

Question 15

summary:
1. g coupeled receptors are linked to —–
2. g coupled proteins can generate varied and complex — cascade
3. —– enzymes targets by activated g protein include: adenylate cyclase and phospholipase c
4. adenylate cyclase and phospholipase c activity differentially regulated by different —–

Answer 15

• hetrotrimetric G proteins
• signalling
• classical effectors enzymes
• G protein c activity