Divalent metal ions induce conformational change in pure, human wild-type p53 tumor suppressor protein

The ability of wild-type and not mutant p53 to exert antiproliferative effects on normal cells may be related to a difference in the conformational state of the protein. We have used pure, human wild-type p53 and a panel of monoclonal antibodies whose epitopes map throughout the protein to assess whether divalent metal ions affect the conformation of p53. Our results show that the presence of Zn2+ ions at physiological concentrations, directly reduced or blocked accessibility of epitopes on pure wild-type p53, an effect which was reversed by chelating agents. Loss of epitope reactivity was maximal between the protein mid-region and C-terminus. Analytical sucrose density gradient ultracentrifugation studies also confirmed that Zn(2+)-induced conformational changes partially affected the pattern of p53 oligomerisation. The observed binding of pure p53 to a sequence-specific DNA motif was unaffected by the presence of added Zn2+ ions or metal chelating agents.