12. Biosignaling

Ras is estimated to be responsible for 30% of human cancers. Most mutations in Ras prevent the protein from binding GTPase-activation proteins (GAPs). What is the effect of this mutation on the signal transduction?

The monomeric G-protein Ras is activated by _______________, while _______________ helps turn Ras off.

All of the following are true in the Ras and MAPK pathway EXCEPT:

Guanine Exchange Factors (GEFs) bind Ras-GDP and promote dissociation of bound GDP to be replaced by GTP. GTPase Activating Proteins (GAPs) bind Ras-GTP and stimulates GTPase activity of Ras. How is the downstream signal affected by the presence of GEFs and GAPs?

Place the insulin RTK signaling events in order from 1-7:

a) Ligand binding results in autophosphorylation of the receptor tyrosine kinase ______.

b) MAPKK (Mek) phosphorylates MAPK (Erk) ______.

c) Sos binds then activates Ras ______.

d) Receptor tyrosine kinase phosphorylate IRS-1, which binds the SH2 domain of Grb2 ______.

e) Ras activates MAPKKK (Raf-1) ______.

f) MAPK (Erk) activates transcription factors to regulate mRNA synthesis ______.

g) MAPKKK (Raf-1) phosphorylates MAPKK (Mek) _______.

In the insulin signaling pathway to activate the protein Ras, activated IRS-1 binds to ___________.

Insulin is one of the hormones/growth factors that will activate the Ras and MAP kinase pathway. Concerning this system, all of the following are true EXCEPT