Chp 17 G-protein signaling

Question 1

GTPases _____ GTP to _____

Answer 1

hydrolyze

GDP

Question 2

G proteins bind to _____

Answer 2

GTP

Question 3

Heterotrimeric G protens have ___ subunits

Answer 3

3 (alpha, beta, gamma)

Question 4

What type of receptors do Heterotrimeric G proteins use?

Answer 4

G-protein linked

Question 5

Ras superfamily G proteins have GTPase activity. T or F?

Answer 5

False - Heterotrimeric G proteins have GTPase activity

Question 6

What type of receptors do Ras superfamily use?

Answer 6

catalytic receptors

Question 7

Of the types of G protein receptors we learned of - which regulate second messengers

Answer 7

Heterotrimeric G proteins

Question 8

Of the G proteins which are used in cell growth, differentiation and replication?

Answer 8

Ras family

Question 9

of the beta gamma and alpha subunits of G proteins which binds GDP/GTP

Answer 9

alpha

Question 10

Which of the G proteins are mainly used for regulating process’ like cell growth, differentiation, and replication

Answer 10

Ras family

Question 11

Once a ligand binds to a G protein coupled receptor what happens next (4 steps)

Answer 11

1. G protein is activated and then activates a G protein regulated enzyme
2. signal is relayed via activation of second messengers (products of catalyzed enzyme) or serine/threonine protein kinases are phosphorylated. Either way the response is amplified and a biological response is created.

Question 12

_____ percent of heterotrimeric G proteins are found in the brain

Answer 12

90%

Question 13

The G protein of a heterotrimeric G protein coupled receptor is always attached to the G protein

Answer 13

False. The unbound receptor is separate from the G protein. It is only when the ligand binds that a conformational change occurs that allows the receptor to associate with the receptor

Question 14

active G alpha protein trades G_P for G_P

Answer 14

GDP for GTP

Question 15

An active G protein activates _____ which converts ___ to _____ and inorganic phosphate

Answer 15

adenylyl cyclase
ATP
cyclic AMP (cAMP)

Question 16

Adenylyl cyclase and phospholipase C are examples of ______ ________

Answer 16

secondary messengers

Question 17

G alpha subunit is associated with the stimulation of glycogen and fat breakdown in the liver, muscle and adipose tissure Tor F?

Answer 17

True

Question 18

_____ converted from ATP by adenylyl cyclase binds to the regulatory subunit of ________ releasing _____ subunits which then _____ proteinsd

Answer 18

cAMP
protein kinase A (PKA)
Catalytic (C)

Question 19

What enzyme converts cAMP to 5’-AMP? What does this do?

Answer 19

Phosphodiesterase

keeps cAMP levels low in the cell

Question 20

What is one way of defining a secondary messenger?

Answer 20

The first NEW thing that is produced from a signal transduction

Question 21

G alpha inhibitors prevent _______ from producing _____ which prevents ______ from being phosphorylated

Answer 21

adenylyl cyclase
cAMP
enzymes

Question 22

What happens when Vibrio cholera alters the G alpha subunit and what effect does this have?

Answer 22

the subunit can no longer hydrolize GTP - the hydrolysis of GTP inactivates the G protein - when the protein can not be inactivated (as is the case with Vibrio cholera) the protein will continue creating adenylyl cyclase…which will continue to turn ATP to cAMP

Question 23

What does Bordetella pertussis do? Does it act on the G alpha inhibitor or the G alpha activator?

Answer 23

Works on the G alpha inhibitor protein by inhibiting it so it can’t break down adenylyl cyclase and so excess cAMP is produced.

Question 24

what is the name given to calcium-binding proteins

Answer 24

calmodulin

Question 25

calmodulin must have calcium bound to effect calcium dependent enzymes T or F?

Answer 25

True

Question 26

When Ras G proteins are activated by GTP what does the signal cascade do? What are RAS proteins important for?

Answer 26

activates gene transcription

Important for cell cycle, mitosis, cell proliferation

Question 27

What does over activity of RAS lead to

Answer 27

Cancer

Question 28

Explain the Ras signaling pathway

Answer 28

1. ligand binds to receptors. This allows the receptors to come together and tyrosine is phosphorylated
2. SH2 docs at the phosphorylated tyrosine receptors (phosphotyrosine)
3. Once SH2 is bound GTP replaces GDP and the Ras protein becomes activated
4. active Ras protein phosphorylates a serine protein kinase
5. A cascade occurs that eventually triggers MEK (MAPK)
6. gene regulating transcription factors are phosphorylated

Question 29

What is the end result of the Ras pathway

Answer 29

Gene regulating transcription factors are phosphorylated

Question 30

What terminates all G protein signal transductions

Answer 30

hydrolysis of GTP to GDP

Question 31

What is the G protein in taste cells? What other pathway uses this G protein?

Answer 31

alpha gustducin

Taste cells in the stomach, small intestine, pancreas