Radical stress can damage biomolecules, leading to alterations often associated to many pathologies. Radical damage to proteins may be of particular importance in vivo, since the loss of protein function may affect for example the activity of enzymes. Moreover, damaged proteins could contribute to secondary damage to other biomolecules. In this context the radical-induced damages on sulfur-containing proteins, such as lysozyme (Lyso), ribonuclease (RNase A) and metallothioneins, were evaluated as well as the possible post-translational mechanism of the damage to another cell compartment, such as lipid domain. Free radical generation was obtained by ??-irradiation. The protein degradation due to radical exposure was evaluated by Raman spectroscopy as well as enzymatic assays. The potential capability of the sulfur-containing proteins in transferring the damage to other biomolecules was evaluated by biomimetic models, containing protein and unsaturated lipid vesicles. These models showed that protein degradation is accompanied by structural alteration of unsaturated lipids, which changed the naturally occurring cis geometry to the trans configuration (Scheme I). In particular, thiyl radicals derived from Met residues are probably the isomerising agent of the double bonds. The protein structure and amino acid content resulted to play a significant role in blocking the ready access of free radicals both to the sulfur-containing residues and the active site, so strongly affecting both the radio-sensitivity of proteins and the potential of the tandem radical damage. For example, the lowest irradiation dose was enough to cause changes in Met residues of RNase A, whereas similar modifications were visible in Lyso only at the highest dose (Fig. 1); of consequence, different isomerisation trends were obtained. A chemical-biology approach based on the radical reductive modifications can be suggested, in order to fully evaluate the proteomic and lipidomic changes associated with cellular stress.
Sulfur-containing proteins under radical stress: damage selectivity and tandem radical potential
A Torreggiani;C Ferreri;C Chatgilialoglu
2007
Abstract
Radical stress can damage biomolecules, leading to alterations often associated to many pathologies. Radical damage to proteins may be of particular importance in vivo, since the loss of protein function may affect for example the activity of enzymes. Moreover, damaged proteins could contribute to secondary damage to other biomolecules. In this context the radical-induced damages on sulfur-containing proteins, such as lysozyme (Lyso), ribonuclease (RNase A) and metallothioneins, were evaluated as well as the possible post-translational mechanism of the damage to another cell compartment, such as lipid domain. Free radical generation was obtained by ??-irradiation. The protein degradation due to radical exposure was evaluated by Raman spectroscopy as well as enzymatic assays. The potential capability of the sulfur-containing proteins in transferring the damage to other biomolecules was evaluated by biomimetic models, containing protein and unsaturated lipid vesicles. These models showed that protein degradation is accompanied by structural alteration of unsaturated lipids, which changed the naturally occurring cis geometry to the trans configuration (Scheme I). In particular, thiyl radicals derived from Met residues are probably the isomerising agent of the double bonds. The protein structure and amino acid content resulted to play a significant role in blocking the ready access of free radicals both to the sulfur-containing residues and the active site, so strongly affecting both the radio-sensitivity of proteins and the potential of the tandem radical damage. For example, the lowest irradiation dose was enough to cause changes in Met residues of RNase A, whereas similar modifications were visible in Lyso only at the highest dose (Fig. 1); of consequence, different isomerisation trends were obtained. A chemical-biology approach based on the radical reductive modifications can be suggested, in order to fully evaluate the proteomic and lipidomic changes associated with cellular stress.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.