Briefly discuss the Ras pathway.

Expert Solution

The MAPK/ERK pathway (Ras-Raf-MEK-ERK pathway) is a chain of proteins in the cell that communicates a signal from a receptor on the cell surface to the DNA in the cell nucleus.The extracellular mitogen binds to the membrane receptor, and allows Ras to swap its GDP for a GTP. It can now activate MAP3K, which is responsible to activate MAP2K, which is responsible to activate MAPK. MAPK is able to activate a transcription factor, such as Myc. Receptor-linked tyrosine kinases like the epidermal growth factor receptor (EGFR) are activated by extracellular ligands. The epidermal growth factor (EGF) binds to the EGFR, and able to activate the tyrosine kinase activity of the cytoplasmic domain of the receptor. The EGFR becomes phosphorylated on tyrosine residues. Docking proteins including GRB2 contain a SH2 domain that is able to bind to the phosphotyrosine residues of the activated receptor. GRB2 can bind to the guanine nucleotide exchange factor SOS by way of the two SH3 domains of GRB2. When the GRB2-SOS complex docks to phosphorylated EGFR, SOS is activated, and this can promote the removal of GDP from a member of the Ras subfamily. Ras may then bind to GTP and become active.

gladiator answered 2 years ago

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