Common Conformational Effects in the P53 Protein of Vinyl Chloride-Induced Mutations

The tumor suppressor gene p53 has been identified as the most frequent site of genetic alterations in human cancers. Vinyl chloride, a known human carcinogen, has been associated with specific A T transversions at codons 179, 249, and 255 of the p53 gene. The mutations result in amino acid substitutions of His Leu at residue 179, Arg Trp at residue 249, and Ile Phe at residue 255 in highly conserved regions of the DNA-binding core domain of the p53 protein. We previously used molecular dynamics calculations to demonstrate that the latter two mutants contain certain common regions that differ substantially in conformation from the wild-type structure. In order to determine whether these conformational changes are consistent for other p53 mutants, we have now used molecular dynamics to determine the structure of the DNA-binding core domain of the Leu 179 p53 mutant. The results indicate that the Leu 179 mutant differs substantially from the wild-type structure in certain discrete regions that are similar to those noted previously in the other p53 mutants. One of these regions (residues 204–217) contains the epitope for the monoclonal antibody PAb240, which is concealed in the wild-type structure, but accessible in the mutant structure, and another region (residues 94–110) contains the epitope for the monoclonal antibody PAb1620, which is accessible in the wild-type structure, but concealed in the mutant structure. Immunologic analyses of tumor tissue known to contain this mutation confirmed these predicted conformational shifts in the mutant p53 protein.