Faculty Collaboration Database

Bicarbonate-dependent peroxidase activity of human Cu,Zn-superoxide dismutase induces covalent aggregation of protein: intermediacy of tryptophan-derived oxidation products. J Biol Chem 2003 Jun 27;278(26):24078-89

Date

04/11/2003

Pubmed ID

12686560

DOI

10.1074/jbc.M302051200

Scopus ID

2-s2.0-0037929802 (requires institutional sign-in at Scopus site)   107 Citations

Abstract

This study addresses the mechanism of covalent aggregation of human Cu,Zn-superoxide dismutase (hSOD1WT) induced by bicarbonate (HCO3-)-mediated peroxidase activity. Higher molecular weight species (apparent dimers and trimers) of hSOD1WT were formed from incubation mixtures containing hSOD1WT, H2O2, and HCO3-. HCO3--dependent peroxidase activity and covalent aggregation of hSOD1WT were mimicked by UV photolysis of hSOD1-WT in the presence of a [Co(NH3)5CO3]+ complex that generates the carbonate radical anion (CO3.). Human SOD1WT has but one aromatic residue, a tryptophan residue (Trp-32) on the surface of the protein. Substitution of Trp-32 with phenylalanine produced a mutant (hSOD1W32F) that exhibits HCO3--dependent peroxidase activity similar to wild-type enzyme. However, unlike hSOD1WT, incubations containing hSOD1W32F,H2O2, and HCO3-did not result in covalent aggregation of SOD1. These findings indicate that Trp-32 is crucial for CO3.-induced covalent aggregation of hSOD1WT. Spin-trapping results revealed the formation of the Trp-32 radical from hSOD1WT, but not from hSOD1W32F. Spin traps also inhibited the covalent aggregation of hSOD1WT. Fluorescence experiments revealed that Trp-32 was further oxidized by CO3., forming kynurenine-type products in the presence of oxygen. Molecular oxygen was needed for HCO3-/H2O2-dependent aggregation of hSOD1WT, implicating a role for a Trp-32-dependent peroxidative reaction in the covalent aggregation of hSOD1WT. Taken together, these results indicate that Trp-32 oxidation is crucial for covalent aggregation of hSOD1. Implications of HCO3--dependent SOD1 peroxidase activity in amyotrophic lateral sclerosis disease are discussed.

Author List

Zhang H, Andrekopoulos C, Joseph J, Chandran K, Karoui H, Crow JP, Kalyanaraman B

Author

Balaraman Kalyanaraman PhD Professor in the Biophysics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Amyotrophic Lateral Sclerosis
Bicarbonates
Dimerization
Dose-Response Relationship, Drug
Electron Spin Resonance Spectroscopy
Humans
Models, Chemical
Oxidation-Reduction
Peroxidases
Protein Conformation
Superoxide Dismutase
Tryptophan