Probing the structure and mechanism of Ras protein with an expand genetic code

Ras - proteins encoded by the mammalian ras proto-oncogene act as a molecular signals for cell growth and differentiation to one or more intracellular effector moleculars.

Model of Ras protein with bound GTP

• The chemical basis for swith function involves the cycling of the protein between the inactive guanosine diphosphate (GDP)-bound state and the active guanosine triphosphate (GTP)-bound state.

• Point mutations that result in a decrease in the intrinsic guanosine triphosphatase (GTPase) activity of Ras are associated with approximately 30% of human tumors.

• To test the molecular mechanisms of switch inactivation (and oncogenic activation) - systematically substituted residues in loop L1 (the phosphate-binding loop) and loop L4 (the switch II region) with a series of unnatural amino acids.

• Incorporation of unnatural amino acids into Ras protein - in vitro suppression of TAG nonsense mutations with a chemically aminoacylated suppressor tRNA.