title: Methionine oxidation stabilizes non-toxic oligomers of alpha-synuclein through strengthening the auto-inhibitory intra-molecular long-range interactions.
abstract: Oxidative stress and aggregation of the presynaptic protein alpha-synuclein (alpha-Syn) are implied in the pathogenesis of Parkinson's disease and several other neurodegenerative diseases. Various posttranslational modifications, such as oxidation, nitration and truncation, have significant effects on the kinetics of alpha-Syn fibrillation in vitro. alpha-Syn is a typical natively unfolded protein, which possesses some residual structure. The existence of long-range intra-molecular interactions between the C-terminal tail (residues 120-140) and the central part of alpha-Syn (residues 30-100) was recently established (Bertoncini et al. (2005) Proc Natl Acad Sci U S A 102, 1430-1435). Since alpha-Syn has four methionines, two of which (Met 1 and 5) are at the N-terminus and the other two (Met 116 and 127) are in the hydrophobic cluster at the C-terminus of protein, the perturbation of these residues via their oxidation represents a good model for studying the effect of long-range interaction on alpha-Syn fibril formation. In this paper we show that Met 1, 116, and 127 are more protected from the oxidation than Met 5 likely due to the residual structure in the natively unfolded alpha-Syn. In addition to the hydrophobic interactions between the C-terminal hydrophobic cluster and hydrophobic central region of alpha-Syn, there are some long-range electrostatic interactions in this protein. Both of these interactions likely serve as auto-inhibitors of alpha-Syn fibrillation. Methionine oxidation affects both electrostatic and hydrophobic long-range interactions in alpha-Syn. Finally, oxidation of methionines by H2O2 greatly inhibited alpha-Syn fibrillation in vitro, leading to the formation of relatively stable oligomers, which are not toxic to dopaminergic and GABAergic neurons.
authors.affiliation: Department of Chemistry and Biochemistry, University of California at Santa Cruz, Santa Cruz, CA 95064, USA.
authors.forename: Wenbo
authors.initials: W
authors.lastname: Zhou
authors.forename: Chunmei
authors.initials: C
authors.lastname: Long
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Reaney
authors.forename: Donato A
authors.initials: DA
authors.lastname: Di Monte
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Fink
authors.forename: Vladimir N
authors.initials: VN
authors.lastname: Uversky
mesh_terms: D019943:Amino Acid Substitution; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008715:Methionine / Q000737:chemistry* / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D051844:alpha-Synuclein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D016877:Oxidants; D051844:alpha-Synuclein; D008715:Methionine; D006861:Hydrogen Peroxide