One-electron oxidation of beta-amyloid peptide: sequence modulation of reactivity.
Amyloid beta peptide (Abeta) is a 39 to 43 amino-acid-long peptide implicated in Alzheimer's disease. One of its mechanisms of toxicity is related to its redox properties. Therefore we studied its one electron oxidation using azide free radicals produced in gamma and pulse radiolysis, and compared the results with those obtained with the reverse sequence Abeta(40-1). HPLC analysis combined with absorption, fluorescence, Raman spectroscopy, and MALDI-TOF MS were used for product identification. Met35 was shown to be the target in Abeta(1-40); oxidation leads to a major compound that is Abeta with methionine sulfoxide. Similarly, oxidation of fragment Abeta(29-40) also leads to methionine sulfoxide. For Abeta(40-1), Met35 is not reactive and Tyr10 is the target of azide radicals. The major products are peptide dimer linked by dityrosine and trimer. The lowering of the one-electron reduction potential of the MetS+/Met couple, which was proposed, is in agreement with our findings. To our knowledge, this is the first time that such a drastic effect of the primary sequence is observed in a small peptide. In addition, it is also the first experimental demonstration of the sensitivity of the one-electron reduction potential of methionine on neighboring groups.
Kadlcik
Vojtech
V
Laboratoire de Chimie Physique, UMR 8000, Université Paris-Sud, 91405 Orsay Cedex, France.
Sicard-Roselli
Cecile
C
Mattioli
Tony A
TA
Kodicek
Milan
M
Houee-Levin
Chantal
C
D000544:Alzheimer Disease / Q000473:pathology*; D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D001386:Azides / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D019281:Dimerization; D004307:Dose-Response Relationship, Radiation; D004583:Electrons; D004591:Electrophoresis, Polyacrylamide Gel; D005609:Free Radicals; D005720:Gamma Rays; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000494:pharmacology; D007477:Ions; D013058:Mass Spectrometry; D008715:Methionine / Q000031:analogs & derivatives* / Q000737:chemistry; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010446:Peptide Fragments / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013053:Spectrophotometry; D013059:Spectrum Analysis, Raman; D014357:Trypsin / Q000494:pharmacology; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry
D016229:Amyloid beta-Peptides; D001386:Azides; D005609:Free Radicals; D007477:Ions; D010446:Peptide Fragments; D010455:Peptides; D014443:Tyrosine; D008715:Methionine; D006861:Hydrogen Peroxide; C007543:dityrosine; D014357:Trypsin; D010100:Oxygen; C013111:methionine sulfoxide