Cancer cells often times have mutations effecting Ras. Which mutations are not l

Question

Cancer cells often times have mutations effecting Ras. Which mutations are not likely to cause cancer?

Wrong Answer:

Those that increase RAS binding to GTP

Answers:

Those that increase RAS binding to SOS

Those that increase RAS binding to GTP

Those that decrease binding to GTP and increase binding to GDP

Cancer cells often times have mutations effecting Ras. Which mutations are not likely to cause cancer?

Wrong Answer:

Those that increase RAS binding to GTP

Answers:

Those that increase RAS binding to SOS

Those that increase RAS binding to GTP

Those that decrease binding to GTP and increase binding to GDP

Explanation / Answer

The mutation in those that decrease binding to GTP and increase binding to GDP do not cause cancer. This is because the Ras protein when bound to GTP is activated by GAP (GTPase activating proteins) and GEF (guanine nucleotide exchange factor) and when GTP is changed to GDP, the Ras protein is inactivated. Thus, a mutation decrease GTP binding with Ras can increase its binding with GDP and hence inactivate Ras protein and so do not cause cancer.

SOS is a GEF and regulates Ras activity by regulating along with GAP.

Ras activity is increased by GTP binding and mutation may further increase GTP binding with Ras and hence, may result in Ras activation and may cause cancer.

Therefore, option 3 is correct.

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