Protein Repair and Degradation

Abstract

Protein oxidation is one of the important processes taking place during oxidative stress. Numerous amino acids can be modified within proteins resulting in a large variety of oxidatively modified proteins. These oxidation reactions are accompanied by secondary unfolding of the proteins and modification by non-protein oxidation products. For maintaining the protein pool two processes must be taken into account: protein repair and protein degradation. The known protein repair mechanisms are limited to a few amino acid modifications. However, special removal systems exist in all cellular compartments for degrading oxidized proteins. The major removal system for oxidized proteins in the nucleus and the cytosol is the proteasomal system. The structure, composition, and function of this proteolytic system will be reviewed here. Severe oxidation, however, leads to the formation of insoluble, non-degradable aggregates. These aggregates accumulate within cells, especially during neurodegenerative diseases and the aging process.