The Three-Dimensional Structure of P21 in the Catalytically Active Conformation and Analysis of Oncogenic Mutants
The three-dimensional crystal structure of the catalytically active, GTP-analogue containing complex of H-ras encoded p21 (aa 1–166) has been determined at 1.35 Å resolution. It has the same topology as the G-binding domain of elongation factor Tu. The structure analysis revealed the binding sites of the nucleotide and of the essential cofactor Mg2+ in great detail and made it possible to propose a mechanism for GTP hydrolysis. In addition to the wild-type protein, the structures of several p21 mutants have been solved. While the overall structures of these proteins are not perturbed, there are small, but significant differences at the positions of the mutated amino acids. In the oncogenic mutants (Gly-12→Arg, Gly-12→Val, Gln-61→Leu, Gln-61→His), these mutations interfere with the proposed mechanism of catalysis and thus lead to a reduced rate of GTP hydrolysis.
KeywordsPhosphate Binding Oncogenic Mutant Aliphatic Side Chain Guanine Base Phosphate Oxygen
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