PKA

Question 1

What amino acids can be phosphorylated

Answer 1

serine, threonine, and tyrosine

Question 2

What are the five basic steps of protein activity regulation?

Answer 2

1. Ligand binding
2. Second messanger
3. Protein kinase cascade
4. Transcription factor phosphorylation
5. mRNA production

Question 3

What is Protein Kinase A (PKA) activated by?

Answer 3

cAMP

Question 4

True or False: All kinases bind to ATP and this is highly conserved?

Answer 4

True

Question 5

True or False: cAMP is synthesized on demand?

Answer 5

True: cAMP levels are low until a. cyclase converts ATP into cAMP.

Question 6

What does Adenylate Cyclase turn on?

Answer 6

it turns on the conversion from ATP to cAMP

Question 7

What turns off cAMP production?

Answer 7

Phosphodiesterases

Question 8

How is interaction specificity achieved?

Answer 8

A. cyclase controls flux of cAMP. this causes a localized rise in cAMP.

Question 9

What are cAMP dependent protein kinases?

Answer 9

they are a family of PKAs that are activated by cAMP. They phosphorylate ser/thr hydroxyl group on target protein

Question 10

What is the phosphorylation consensous for cAMP dependent Protein Kinases?

Answer 10

Arg-Arg-X-Ser

Question 11

What Amino Acid can be used as a peptide inhibitor?

Answer 11

Alanine can be used as it is similar to Serine. It was used in crystal structure observations

Question 12

What is highly conserved about PKA

Answer 12

*The proteins sequences/motifs.
*the Asp is highly conserved and involved in binding the terminal phosphate of ATP

Question 13

What are some features of the crystal structure of PKA?

Answer 13

*the highly conserved ATP binding region
*they are bilobal with a hinge region that allow the unit to change from open/active to closed/inactive
*it has three conserved glycine residues on the N lobe that form a loop where ATP binds
*the terminal gamma phosphate of ATP interacts with a conserved Asp residue on the lower domain

Question 14

What are the 4 parts of the PKA Catalytic subunit (C unit)

Answer 14

*N-lobe (has 3 gly residues)
* C-lobe (has substrate binding groove)
*Hinge region (opens and closes, allows ATP to bind)
*Catalytic cleft (where ATP is hydrolysis occurs)
*Substrate binding region

Question 15

What are the physical properties of cAMP dependent protein kinases(CDPK)

Answer 15

its tetrameric protein with two regulatory subunits (R) and two catalytic subunits (C). When the protein is active the C subunits separate and the Two R units stay a dimer. The R units are a dimer even when inactive and are bound by a disulfide bond.

Question 16

What does CDPK do?

Answer 16

it mediates the effects of the second messenger, cAMP.

Question 17

What is the Mechanism of action for CDPK?

Answer 17

pseudosubstrate/ inhibitor domain

Question 18

How is the PKA activated by cAMP?

Answer 18

The C subunits are bound to the R subunits via a substrate binding domain on the C unit that interacts with the pseudo-substrate domain on the R unit. 2 cAMP molecules (per R unit) co operatively bind to the R subunit, this weakens the interaction between the R and C units, causing them to dissociate from eachother. The now free C subunits can phosphorylate protein in their vacinity.

Question 19

Once activated, what does a PKA do?

Answer 19

it often Phosphorylates TF in the nucleus. This is done by binding to the nucleus. it then activates CREB which turns on TF that lead to gene expression

Question 19

What is an AKAP

Answer 19

An AKAP is an anchoring protein that contains multiple domains that interact with proteins and structures like the ER, this is its main function. It tethers proteins in place and allows for a localized production of cAMP. Its important in cross talk and bringing things together to create signaling complexes. it also acts as scaffolding.

Question 20

What have structural studies taught us about how catalytic domains and their functions?

Answer 20

it taught us that the ATP binding region is conerved. that they are bilobal with a hinge region that allows for movement. that they contain 3 conserved glycine residues from form the ATP binding region. Look at hand drawn pic of the C and R subunits!

Question 21

How is PKA activity regulated in space?

Answer 21

PKA is anchored to AKAPS. AKAPS tether the PKA to sub cellular structures like the ER and have a tail region that allows for binding to the R subunits of PKA. AKAPS bind other proteins associated with signal transduction such as PKC and phosphatases