Oxidation of methionine residue at hydrophobic core destabilizes p53 tetrameric structure

The tumor suppressor protein p53 is a tetrameric phosphoprotein that induces cell cycle, development, and differentiation by regulating the expression of target genes. The tetramerization of p53 is essential for its tumor suppressor functions. It has been known that oxidation of proteins affects their structure and function. A methionine residue (Met340) is located at the hydrophobic core in p53 tetramerization domain. Here, we demonstrated that Met340 residue can be oxidized to methionine sulfoxide under oxidative conditions and investigated effects of the oxidation of p53 tetramerization domain on its stability and oligomerization state by CD measurement and gel filtration. The oxidation of Met340 drastically induced destabilization of the p53 tetramer by 22.8 kJ/mol of ΔΔG Tm , while retaining the identical conformation as that of the wild‐type peptide. Trypsin digestion experiments also showed that oxidation of Met340 allowed the peptide to form locally loose structure and become more sensitive to enzyme degradation. The tetrameric structure may be destabilized because the oxidation of Met340 induces charge repulsion and/or steric hindrance between the sulfoxide groups. These results taken together suggested that oxidation of methionine residues in the p53 protein might be one of the inactivation mechanisms of p53 transcriptional function under conditions of oxidative stress. © 2008 Wiley Periodicals, Inc. Biopolymers 91: 78–84, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com