The Ras superfamily of GTPases, named after the rat sarcoma viral oncogene, contains many Ras isoforms including K-Ras, H-Ras and N-Ras. The three isoforms are expressed at different levels in different types of cells. In general, activating mutations of at least one of these isoforms are present in 15% of all cancers. Switching from an active or resting state, Ras can either bind GTP or GDP respectively. In the triphosphate conformation, Ras will interact with GTPase activating protein (GAP) to increase its activity. Mutations in any of the three isoforms can convert these proteins into active oncogenes. Additionally, Ras mutations are found in 30 % of all human cancer.
