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 tit 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 oil 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 Delta Delta G (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. Tit(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 tit the p53 protein might lie one of the inactivation mechanism of p53 transcriptional function under conditions of oxidative stress. (C) 2008 Periodicals, Inc. Biopolymers 91: 78-84, 2009.