Question

How is Ras activated and How is ERK activated by Ras signaling?

Answer 1

In ERK Signalling pathway, receptor linked tyrosine kinases are the receptors that initiates the signalling. Tyrosine kinases such as epidermal growth factor receptor binds with its ligand epidermal growth factor and phosphorylates it's cytoplasmic domain to get activated . Once activated Grb2 docks with the activated egfr through Sh2 Domain and binds with guanine nucelotide exchange factor SOS through Sh3 domains

Once bound SOS removes GDP that is associted with ras so that it can bind with GTP and become activated

Once ras is activated it binds with raf and phosphorylates to activate Raf and than raf phosphorylates MEK to activate it

MEK activates MAPK or extracellular signal regulated kinases (ERK) by phosphorylating it