title: Oxidation of methionine residue at hydrophobic core destabilizes p53 tetrameric structure.
abstract: 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 DeltaDeltaG(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.
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Nomura
authors.forename: Rui
authors.initials: R
authors.lastname: Kamada
authors.forename: Issaku
authors.initials: I
authors.lastname: Ito
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Chuman
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Shimohigashi
authors.forename: Kazuyasu
authors.initials: K
authors.lastname: Sakaguchi
mesh_terms: D002850:Chromatography, Gel; D002942:Circular Dichroism; D057927:Hydrophobic and Hydrophilic Interactions; D008715:Methionine / Q000378:metabolism*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011489:Protein Denaturation; D055503:Protein Multimerization; D055550:Protein Stability; D020836:Protein Structure, Quaternary; D013816:Thermodynamics; D014357:Trypsin / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D010455:Peptides; D016159:Tumor Suppressor Protein p53; D008715:Methionine; D014357:Trypsin