Question

Ras Homework Namea due April 23, 2019 Cell Proliferation ReceptorRas ERK Tyrosine Kinase Wild type Off cells without growth factor Wild typeOn cells with growth factor Mutations that keep Ras in the GTP- bound form Mutations that keep Ras in the GDP. bound form Mutations that No proliferation GDP-bound Inactive, Not phosphorylated Phosphorylated GTP-bound Active Proliferation inactivate GAP Mutations that overexpress RTK

What is the answers for this chart? Thanks!

Answer 1

Ras is a monomeric GTpase switch protein that cycles between an inactive GDP bound form and active GTP bound form. Now in case 1.

Mutation that keep Ras in GTP bound form- Receptor tyrosine kinase is ON., Ras in in GTP bound state, ERK active and phosphorylated, and their will be overproliferation of cells.

2. Muation that keeps Ras in GDP bound-- Receptor tyrosine kinase will be on but will not able to activate Ras. So Ras will be GDP bound state, ERK inactive and nonphosphorylated, No cell proliferation.

3. Mutation that inactivates GAP:  GAP is GTpase activating protein which accerates GTP hydrolysis in Ras. So it will not able to bind to activated RTks if it is inactivated by mutation.Now RTK is activated, Ras is GTP bound, ERK is phosphorylated and cell prolferation will be there.

4.Mutation that overexpresses RTKs: If there is overexpression of RTKs they can dimerize in the absence of ligand thus stimulating cell division inappropriate times. So overexpression of RTK leads to RTKs activated, Ras in GTP bound form., ERK activated and phosphorylated and overproliferation of cells.