Cell Signaling Problem Set
Problem 9: G-proteins
Tutorial to help answer the question
The endogenous GTPase activity of G-proteins serves to:
Cellular responses to signals must be reversible. Ras is a G protein that is activated by exchanging GTP for bound GDP. The endogenous GTPase of Ras degrades the GTP back to GDP, inactivating the protein.
In some forms of cancer, mutations in Ras decrease the endogenous GTPase activity. The normal form of Ras is called a proto-oncogene and the mutant version an oncogene. Permanently activated Ras leads to unregulated cell division in the cancer.
The Biology Project
Department of Biochemistry and Molecular Biophysics
University of Arizona
Revised: August 2004
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