Three-dimensional structure of p21H-ras and its implications.

The three-dimensional structure of the H-ras oncogene product p21 has been determined in both its active, GTP-bound and its inactive, GDP-bound forms. This has supplied a wealth of information on the mode of binding of guanine nucleotides, on the mechanism of the GTPase reaction and on the conformational change of the protein which accompanies GTP hydrolysis. The structural analysis has also given clues to the interaction of p21 with the regulatory proteins GAP (GTPase Activating Protein) and nucleotide exchange factor. The three-dimensional structures of oncogenic mutants of p21 have also been determined and can nicely explain different biochemical and biological behaviour of these mutant proteins.