molecular signalling

Question 1

why is phosphorylation important in signalling pathways

Answer 1

it regulates the degradation of proteins and cell cycle

Question 2

what does the catalytic domain of the kinase fold into

Answer 2

2 lobed structures:
N-terminal lobe (small)
- ATP binding loop binds ATP
C-terminal lobe (large)
- catalytic loop binds target protein (substrate)

Question 3

what are the types of protein kinases

Answer 3

SERINE/THREONINE:
- cytoplasmic serine/threonine kinases
(MAPK, AKT, PKA, PKC)
- receptor serine/threonine kinases
(receptors from transforming growth factor (TGF)BRI & TGFBRII
TYROSINE:
- membrane
(found inserted in plasma membrane, i.e. receptors tyrosine kinases, e.g. EGFR OR associated with membrane receptors, e.g. JAK)
- cytoplasmic tyrosine kinases
(SRC)

Question 4

what are the types of regulation of kinase activity (provide short explanations and examples)

Answer 4

1. Regulatory (inhibitory) domain
   Some kinases have an inhibitory domain that is part of the same polypeptide chain as the catalytic domain.
   This domain prevents kinase activity until the right signal is received.
   Examples: SRC tyrosine kinase, Ca²⁺ Calmodulin protein kinase.
2. Regulatory subunit
   Some kinases are inhibited by a separate regulatory subunit, a different polypeptide that blocks the active site.
   Example: Protein Kinase A (PKA).
3. Binding of another protein
   Some kinases require binding to another protein for activation.
   Example: Cyclin-Dependent Kinases (CDKs), which need cyclin binding to become active.

Question 5

what are the types of phosphatases

Answer 5

• phosphoserine/threonine phosphates
• phosphotyrosine phosphatases