1 - Oncoproteins and tumour suppressors in the receptor tyrosine kinase signalling pathway

Question 1

G protein:

Answer 1

Protein that can bind GTP or GDP. When GDP bound it is inactive and when GTP bound it is active, due to a shape change because of the additional phosphate. They also have GTPase activity which means that they have the enzymatic ability to remove the terminal phosphate on GTP converting it to GDP.

Question 2

GEF:

Answer 2

Guanine nucleotide exchange factor which exchanges a GDP for GTP on RAS and activates it. Binds to the adaptor protein.

Question 3

MAPK:

Answer 3

Mitogen activated protein kinase. Final kinase activated in the MAPK signalling pathway.

Question 4

Mitogen:

Answer 4

Signalling molecule that causes cell to go through mitosis i.e. stimulates the cell cycle.

Question 5

PI3K:

Answer 5

Phosphoinositide 3 kinase. Lipid kinase that binds to the phosphorylated RTK tail and phosphorylates PIP2 in the membrane to produce PIP3.

Question 6

PTEN:

Answer 6

(Phosphatase and tensin homologue deleted on chromosome ten) Phosphatase that removes phosphate from PIP3 and converts it back to PIP2 thus switching off the PI3K pathway.

Question 7

Receptor Tyrosine Kinase (RTK):

Answer 7

receptor in the membrane that has tyrosine kinase activity. It is activated by dimerization and can then phosphorylate the monomer to which it is bound on a tyrosine amino acid. E.g. epidermal growth factor receptor