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Abstract

The GTP binding domain of the c−Ha−ras protooncogene product (p21'c) and the corresponding region from an oncogenic mutant form of the protein in which glycine at position 12 has been replaced by valine [p21'(G12V)] have been crystallized with P3−1−(2−nitro)penylethylguanosine 5'−O−triphosphate (caged GTP) at their active sites. The crystals give x−ray diffraction patterns to a resolution of better than 0.3 nm. Photolysis can be achieved in the crystal, after which GTP hydrolysis takes place at the rate expected from solution studies. Complete x−ray data sets have been obtained for the starting caged−GTP state and the final GDP state after photolysis and hydrolysis, demonstrating the feasibility of time−resolved structural investigations of the process of GTP hydrolysis