GEF (guanine nucleotide-exchange factor) and GAP (GTPase activating protein) are two regulating proteins of RAS. However, these proteins are in turn regulated by other regulatory proteins. Which change in GAP and GEF can result in excessive proliferation of cells?
P. A permanently active GAP
Q. A nonfunctional GAP
R. Anonfunctional GEF
S. A permanently active GEF
a. Only P
b. P and Q
c. Q and S d. Only S
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The change in GAP and GEF that can result in excessive proliferation of cells: Option C ( Q and S)
- The signal-transduction protein Ras is a member of the family of small G proteins or small GTPases. It is anchored at the inner surface of the plasma membrane by a covalently attached lipid group.
- Ras regulates cell growth through serine or threonine protein kinase.
- GAP (GTPase-activating proteins) is a signaling enzyme that stimulates the hydrolysis of the bound GTP which inactivates the G protein, terminating the signal and shortening the duration of a G protein-mediated response. In short, GAP is responsible for the termination of the signal and returning the system to an inactive state.
- GEF (Guanine nucleotide-exchange factors) are proteins that bind to inactive monomeric G protein and cause dissociation of the bound GDP allowing the G protein to bind to a GTP thus activating the G protein. In short, GEF is responsible for the activation of the G protein.
- For an excessive proliferation of cells, the terminating protein should remain inactive while the activating protein should remain active.
- Thus the combination of a nonfunctional GAP and a permanently active GEF will result in excessive proliferation of cells. Hence both statements Q and S are true.
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