title: Sulphur Atoms from Methionines Interacting with Aromatic Residues Are Less Prone to Oxidation.
abstract: Methionine residues exhibit different degrees of susceptibility to oxidation. Although solvent accessibility is a relevant factor, oxidation at particular sites cannot be unequivocally explained by accessibility alone. To explore other possible structural determinants, we assembled different sets of oxidation-sensitive and oxidation-resistant methionines contained in human proteins. Comparisons of the proteins containing oxidized methionines with all proteins in the human proteome led to the conclusion that the former exhibit a significantly higher mean value of methionine content than the latter. Within a given protein, an examination of the sequence surrounding the non-oxidized methionine revealed a preference for neighbouring tyrosine and tryptophan residues, but not for phenylalanine residues. However, because the interaction between sulphur atoms and aromatic residues has been reported to be important for the stabilization of protein structure, we carried out an analysis of the spatial interatomic distances between methionines and aromatic residues, including phenylalanine. The results of these analyses uncovered a new determinant for methionine oxidation: the S-aromatic motif, which decreases the reactivity of the involved sulphur towards oxidants.
authors.affiliation: Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Universidad de Málaga, 29071-Málaga, Spain.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Aledo
authors.affiliation: Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Universidad de Málaga, 29071-Málaga, Spain.
authors.forename: Francisco R
authors.initials: FR
authors.lastname: Cantón
authors.affiliation: Departamento de Lenguajes y Ciencias de la Computación, Universidad de Málaga, 29071-Málaga, Spain.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Veredas
mesh_terms: D000595:Amino Acid Sequence; D024322:Amino Acids, Aromatic / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry; D005974:Glutamate-Ammonia Ligase / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D008715:Methionine / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D013455:Sulfur / Q000737:chemistry
chemical_list: D024322:Amino Acids, Aromatic; D001426:Bacterial Proteins; D016877:Oxidants; D013455:Sulfur; D008715:Methionine; D006861:Hydrogen Peroxide; D005974:Glutamate-Ammonia Ligase