Extra Credit -2 pts total PGDF is a paracrine signaling factor which binds to a specific tyrosine kinase receptor, PGDF receptor. Activation of the...

When activated by the signal, the platelet-derived growth factor (PDGF) receptor phosphorylates itself on multiple tyrosines (as indicated below by the circled Ps; the numbers next to these Ps indicate the amino acid number of the tyrosine). These phosphorylated tyrosines serve as docking sites for proteins that interact with the activated PDGF-receptor. These proteins are indicated in the figure below, and include the proteins A, B, C, and D. The PDGF-receptor is activated when it binds to the signal, PDGF. One of the cellular responses to PDGF is an increase in DNA synthesis, which can be measured by incorporation of radioactive thymidine into the DNA.