explain simply

RTK Signaling through MAPK pathway (also called ERK1 /2 pathway) 1 Insulin receptor binds insulin and undergoes autophosphorylation on Insulin its carboxy!-terminal Tyr residues. B + Insulin receptor phosphorylates IRS-1 P on its Tyr residues. Cytosol P P SH2 domain of Grb2 binds to P -Tyr of IRS-1. Sos binds to Grb2, RAS - GTPase IRS-1 IRS-1 then to Ras, causing GDP release P P Grb 2 GDP and GTP binding to Ras. Sos A GTP Ras changes MEK $Raf - 1 4 Activated Ras binds and activates Raf-1. GDP ~ GTP Nucleus P MEK 5 Raf-1 phosphorylates SRF Elk1 MEK on two Ser residues, activating it. MEK ERK ERK ERK phosphorylates ERK on a The and a Tyr residue, activating it. SRF Elk1 P anybody DNA 6 ERK moves into the nucleus MRNA and phosphorylates nuclear * ERK1 /2 phosphorylating TFs (Elk, SRF, Protein transcription factors such as , activating them. Ets, c-Fos) is well defined mechanism Phosphorylated Elk1 joins SRF of regulation of gene expression to stimulate the transcription and translation of a set of genes needed for cell division. ERK2 can bind to DNA and inhibit other TFs from binding Figure 12-19 Lehninger Principles of Biochemistry, Seventh Edition 2017 W. H. Freeman and Company