When activated by the extracellular signal protein platelet-derived growth facto

Question

When activated by the extracellular signal protein platelet-derived growth factor (PDGF), the PDGF receptor
phosphorylates itself on multiple tyrosines (as indicated in Figure 16-46A 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, and include the
proteins A, B, C, and D. One of the cell’s responses to PDGF is an increase in DNA synthesis, which can be
measured by the incorporation of radioactive thymidine into the DNA.
To determine which protein or proteins, A, B, C, or D, are responsible for the activation of DNA synthesis, you
construct mutant versions of the PDGF receptor that retain one or more tyrosine phosphorylation sites. You
express these mutant versions in cells that do not make their own PDGF receptor. In these cells, the various mutant
versions of the PDGF receptor are expressed normally, and, in response to PDGF binding, become phosphorylated
on whichever tyrosines remain. You measure the level of DNA synthesis in cells that express the various mutant
receptors and obtain the data shown in Figure 16-46B.
A. From these data, which, if any, of proteins A, B, C, and D are involved in the stimulation of DNA synthesis by
PDGF?
Explain your answer.
B. Which, if any, of these proteins inhibit DNA synthesis? Explain your answer.
C. Which, if any, of these proteins seem to have no detectable role in DNA synthesis? Explain your answer.
A is P13k, B is GAP, C is PTP, and D is PLC gamma

[IMG]http://i177.photobucket.com/albums/w210/badboyr6/pdgf.png[/IMG]

Explanation / Answer

In the post, the diagram is not clearly explained. A,B,C, D are not labelled. Please post the question a bit clearly, so that i can help you in answering it. Thank you.

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