By escaping the cell's antioxidant defences, free radicals can damage biomolecules, including proteins, leading to modifications involved in many degenerative diseases. In fact, the exposure of proteins to free radicals may cause structural and functional changes. In particular, a single radical event that leads to an initial damage involving sulfur-containing amino acid residues could produce a reactive species able to damage another cell compartment such as lipid domains. To elucidate the effects of radical stress exposure on the overall protein structure, several aspects were considered: (1) structural changes in sulfur-containing proteins (lysozyme, ribonuclease, and metallothioneines) induced by the radical attack; (2) enzymatic assays to detect the changes in the protein functional activity after radical exposure; (3) tandem radical potential of the sulfur-containing proteins in translating the damage to other biomolecules. Free radical generation, mimicking an endogenous radical stress, was obtained by ?-irradiation of aqueous solutions. By changing the appropriate conditions of irradiation, a selection of the reacting radical species was carried out. The protein degradation due to radical exposure was evaluated by Raman spectroscopy as well as by enzymatic assays [1]. In fact, Raman spectrum can provide valuable information on amino acid side chains (i.e. S-S, Tyr, Trp, Cys-Metal) and conformational changes in the protein secondary structure. Biomimetic models, containing protein and unsaturated lipid vesicles, were used to evaluate the role of sulfur-containing residues of proteins in translating the damage to other biomolecules [1,2]. They showed that protein degradation is accompanied by structural alteration of unsaturated lipids forming liposome vesicles, which changed the naturally occurring cis geometry to the trans configuration (Fig. 1). Thiyl radicals, derived from sulfur-containing residues and able to diffuse through the lipid bilayer, are probably the isomerising species of the double bonds. Protein structure and amino acid content resulted to play an important role in blocking the ready access of free radicals both to the sulfur-containing residues and the active site, so strongly affect both the radio-sensitivity of proteins and the potential of the tandem radical damage.
Structural Lesions of Sulfur-containing Proteins caused by Radical Stress: Assessment and Tandem Radical Potential
A TORREGGIANI;
2007
Abstract
By escaping the cell's antioxidant defences, free radicals can damage biomolecules, including proteins, leading to modifications involved in many degenerative diseases. In fact, the exposure of proteins to free radicals may cause structural and functional changes. In particular, a single radical event that leads to an initial damage involving sulfur-containing amino acid residues could produce a reactive species able to damage another cell compartment such as lipid domains. To elucidate the effects of radical stress exposure on the overall protein structure, several aspects were considered: (1) structural changes in sulfur-containing proteins (lysozyme, ribonuclease, and metallothioneines) induced by the radical attack; (2) enzymatic assays to detect the changes in the protein functional activity after radical exposure; (3) tandem radical potential of the sulfur-containing proteins in translating the damage to other biomolecules. Free radical generation, mimicking an endogenous radical stress, was obtained by ?-irradiation of aqueous solutions. By changing the appropriate conditions of irradiation, a selection of the reacting radical species was carried out. The protein degradation due to radical exposure was evaluated by Raman spectroscopy as well as by enzymatic assays [1]. In fact, Raman spectrum can provide valuable information on amino acid side chains (i.e. S-S, Tyr, Trp, Cys-Metal) and conformational changes in the protein secondary structure. Biomimetic models, containing protein and unsaturated lipid vesicles, were used to evaluate the role of sulfur-containing residues of proteins in translating the damage to other biomolecules [1,2]. They showed that protein degradation is accompanied by structural alteration of unsaturated lipids forming liposome vesicles, which changed the naturally occurring cis geometry to the trans configuration (Fig. 1). Thiyl radicals, derived from sulfur-containing residues and able to diffuse through the lipid bilayer, are probably the isomerising species of the double bonds. Protein structure and amino acid content resulted to play an important role in blocking the ready access of free radicals both to the sulfur-containing residues and the active site, so strongly affect both the radio-sensitivity of proteins and the potential of the tandem radical damage.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
