signaling serine-threonine kinases and phosphotases

Question 1

kinase function:

Answer 1

phosphorylation

Question 2

phosphatase function

Answer 2

dephosphorylation

Question 3

which AA can be phosphorylated? and why?

Answer 3

ser
thr
tyr
because they have a OH group

Question 4

A “closed conformation” of the glycine rich loop in the small lobe forces the ____
and is a ___ reaction

Answer 4

γ-Phosphate of the ATP into the right position for phosphorylation

(a fast reaction)

Question 5

An “open conformation” of the glycine rich loop then allow ____ and is a ___ reaction

Answer 5

exchange of the generated ADP for a new ATP

(a slow reaction).

Question 6

kinase activity is thought to require _____conformations

Answer 6

alternating open and closed

Question 7

“MAP kinase cascades” are examples of ____

Answer 7

how kinases are activated by other “upstream” kinases

Question 8

CaMKII and Calcineurin (a Ca2+ regulated

Answer 8

kinase and phosphate, respectively) are important mediators of long term potentiation and long term depression (LTP and LTD) of synaptic strength, respectively

Question 9

Substrate protein:

Answer 9

Myosin light chain kinase (MLCK), Phosphorylase kinase, EF2 kinase, etc.
but several kinases have many substrates (PKA, PKC, CaMKII)

Question 10

activating stimulus

Answer 10

mitogen activated protein kinase (MAPK)

Question 11

receptor linked

Answer 11

EGF receptor, insulin receptor

Question 12

second messenger

Answer 12

PKA
PKC
caMKII

Question 13

cyclins

Answer 13

CDK2

Question 14

AGC:

Answer 14

PKA, PKG and PKC containing

Question 15

CAMK:

Answer 15

CaM kinases such as CaMKII, MLCK…

Question 16

CMGC:

Answer 16

CDKs, MAPKs (erk, jnk, p38…), GSK3, CLKs CDK MAPK

Question 17

STE:

Answer 17

Ste7,11,20 homologues (MAPK upstream kinases) CK1: Casein kinase 1…

Question 18

TK:

Answer 18

Tyr kinases; TLK: Tyr kinase-like

Question 19

ATP contains energy rich bonds:

Answer 19

energy equivalent, phosphate donor, nucleotide,

conversion to second messenger (cAMP), neuromodulator.

Question 20

Phosphorylation is a _____ attack of the _____

Answer 20

nucleophilic

hydroxyl group (of an S/T) to the γ-P of ATP

Question 21

close conformation:

Answer 21

Glycine loop positions γ-P for phosphorylation reaction (>500 sec–1)

Question 22

open conformation:

Answer 22

Glycine loop allows exchange of ADP with ATP (~20 sec–1)

Question 23

Usually at least 2 of the 4 ____ in inactive state:

Answer 23

distorted

1. Activation loop
2. C helix
3. Glycine rich loop (incl. stable open or close conformation)
4. “ATP binding pocket”

Question 24

inhibitory protein interaction

Answer 24

PKA

Question 25

activating protein interaction

Answer 25

CDK2

Question 26

kinase: PKA

phos required by:

Answer 26

PKA

Question 27

kinase: PKC

phos required by:

Answer 27

PDK1 (phospoinosite-dependent)

Question 28

kinase: PKC

phos required by:

Answer 28

PDK1

Question 29

Calcineurin (PP2B):

Cyclosporin:

Answer 29

immunosuppressant indicated against graft rejection after transplantation.
(in some cases for acute treatment of auto-immune diseases, i.e. psoriasis, Crohn’s disease)

Question 30

Calcineurin (PP2B): Tacrolimus=

Answer 30

FK506: rescue therapy in patients with rejection despite Cyclosporin treatment. Both bind to an “immunophilin” (cyclophilin for cylcosporin; FKBP-12 = FK506 binding protein for tacrolimus) which then inhibits phosphatase activity of Calcineurin.

Question 31

mTOR (mammalian target of rapamycin):

Sirolimus = rapamycin = rapamune:

Answer 31

immunosuppressant; can be used in combination with additional drugs in case of high risk for calcineurin inhibitor associated nephrotoxicity.
Binds to FKBP-12 which then inhibits kinase activity of mTOR (not phosphatase activity of calcineurin)