L14- Phosphotyrosine-based cell signalling

Question 1

what mediates intracellular signalling

Answer 1

signalling proteins:
* Enzymes - kinases, phosphatases, lipases etc
* Adaptors & scaffold proteins (multi-adaptors) - no intrinsic
enzymic activity
* Docking molecules - receptor substitutes
small molecule “messengers”:
* PIP3, IP3, DAG

Question 2

how is intracellular signalling propogated

Answer 2

• uses protein-protein (or
  protein-phospholipid) interactions controlled by phosphorylation
• Interactions are mediated by modular binding domains within proteins these Modules interact with motifs

Question 3

4 modular domains in signal propogation

Answer 3

1. SH2
2. PTB
3. SH3
4. PH

Question 4

SH2 domain

Answer 4

Src Homology 2 domain
- globular domain of ~100 residues
- SH2 domains bind phosphorylated
tyrosine residue (pY) within a motif
- interactions can be intra-molecular (folds protein) or inter-molecular

Question 5

examples of SH2 domain proteins

Answer 5

Src, PI3K, PLCγ, Grb2

Question 6

binding of SH2 domain

Answer 6

scans the residue sequence for a phosphorylated tyrosine and 3 specific C-ter residues

Question 7

PTB domain

Answer 7

Phosphotyrosine-binding domain
- ~150 residues

Question 8

binding of PTB domain

Answer 8

interacts with motif containing a pY residue following a specific N-ter NPX
sequence
N- -4 - Asn - Pro - X - pY - +1 - C
~ 60 PTB domains

Question 9

examples of proteins with PTB domains

Answer 9

IRS1, Shc

Question 10

SH3 domain

Answer 10

Src-Homology 3 domain
- domain of ~60 residues
- motif is common in cytoskeletal proteins - cell division and movement

Question 11

binding of SH3 domain

Answer 11

Phosphorylation independent - no pY
Interacts with proline-rich motifs (PXXP)
N— Pro – X – X – Pro —C

Question 12

examples of SH3 domain containing proteins

Answer 12

Src, Nck, Grb2

Question 13

PH domain

Answer 13

Pleckstrin homology domain
- ~120 residues

Question 14

PH domain binding

Answer 14

binds to phosphorylated inositol phospholipids - PIPs PIP2 & PIP3

PIP2 or PIP3 head groups remain
attached to phospholipid molecules at the plasma membrane –> cytosolic PH domain-containing proteins are
recruited to the plasma membrane upon RTK activation and signalling

Question 15

examples of PH containing proteins

Answer 15

Akt, PDK1, PLCγ

Question 16

c-Src protein structure - enzyme

Answer 16

unique sequence - SH3 - SH2 - PxxP - tyrosine kinase

Question 17

SHP2 protein structure - enzyme

Answer 17

SH2 - SH2 - Phosphatase

Question 18

IRS1 - docking protein structure

Answer 18

PH - PTB - tyrosine residues

Question 19

Nck adapter protein structure

Answer 19

SH3 - SH3 - SH3 - SH2