Mass spectral evidence for carbonate-anion-radical-induced posttranslational modification of tryptophan to kynurenine in human Cu, Zn superoxide dismutase. Free Radic Biol Med 2004 Dec 15;37(12):2018-26
Date
11/17/2004Pubmed ID
15544920DOI
10.1016/j.freeradbiomed.2004.08.026Scopus ID
2-s2.0-8544240825 (requires institutional sign-in at Scopus site) 34 CitationsAbstract
Previously, we showed that oxidation of tryptophan-32 (Trp-32) residue was crucial for H(2)O(2)/bicarbonate (HCO(3)(-))-dependent covalent aggregation of human Cu,Zn SOD1 (hSOD1). The carbonate anion radical (CO(3)(-))-induced oxidation of Trp-32 to kynurenine-type oxidation products was proposed to cause the aggregation of hSOD1. Here we used the matrix-assisted laser desorption ionization-time of flight mass spectroscopy, high-performance liquid chromatography-electrospray ionization mass spectroscopy, and liquid chromatography mass spectroscopy methods to characterize products. Results show that a peptide region (31-36) of hSOD1 containing the Trp-32 residue (VWGSIK) is oxidatively modified to the N-formylkynurenine (NFK)- and kynurenine (Kyn)-containing peptides (V(NFK)GSIK) and (V(Kyn)GSIK) during HCO(-)-dependent peroxidase activity of hSOD1. Also, UV photolysis of a cobalt complex that generates authentic CO(3)(-) radical induced a similar product profile from hSOD1. Similar products were obtained using a synthetic peptide with the same amino acid sequence (i.e., VWGSIK). We propose a mechanism involving a tryptophanyl radical for CO(3)(-)-induced oxidation of Trp-32 residue (VWGSIK) in hSOD1 to V(NFK)GSIK and V(Kyn)GSIK.
Author List
Zhang H, Joseph J, Crow J, Kalyanaraman BAuthor
Balaraman Kalyanaraman PhD Professor in the Biophysics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnionsCarbonates
Chromatography, High Pressure Liquid
Copper
Electron Spin Resonance Spectroscopy
Free Radicals
Humans
Kynurenine
Models, Molecular
Oxidation-Reduction
Protein Processing, Post-Translational
Protein Structure, Tertiary
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
Superoxide Dismutase
Tryptophan
Zinc