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RAS - just starting - under construction

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    1. Where is Ras located in the cell?  What causes Ras to be localized here?

    2. How does Ras get activated?

    3. What are the three dimensional differences between GDP and GTP bound Ras.  Why is the GTP bound form “active?”

    4. What does Ras bound to GTP bind to?  What are the net effects of this in terms of signal transduction?

    5. What reaction does Ras catalyze as an enzyme?

    6. What type of reaction is a GAP catalyzing? GEF? 

      a. Are they opposite reactions? What is different (enzymatic control)
    7. GAP is an acronym for GTPase activating protein. What GTPase is being activated?

    8. Would RAS “turn off” without a GAP present? Why is this critical?

    9. What molecule (GTP or GDP) would be bound to RAS if there were no GAPs or GEFs present? Why?

    10. Why does a GAP increase the enzymatic activity RAS?  What does a GAP provide that aids in the chemistry of the reaction?

    https://www.ncbi.nlm.nih.gov/pmc/art...%20Ras%20cycle.

    Paper about targeting phosphorylation and cancer therapy:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8642438/

    1. Ras can be phosphorylated at Tyr 32 and Tyr64 by Src kinase, which leads to inhibition of binding to Raf and increased GTP hydrolysis.  Provide a rationale for why this post-translational modification plays a role in the overall function of Ras.  (Not sure what to ask here- there seems to be a number of kinases involved that do different things as explained in the paper above)

    2.  There are mutations in Ras, including Gly 12, Gly13, and Gln 61 which impair GTPase activity and GAP-mediated GTP hydrolysis.  Predict what changes this would cause in the cell.
    3. Think about designing a small molecule drug that affects the Ras signaling pathway and treats cancer.  What proteins could you target?  For each protein target,  should the drug increase or decrease the activity of its target?  Explain your answers.

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