Post-translational mutation of sulfur-containing amino acid in the protein sequence via radical damage is an interesting field of investigation, although the easiness to find out the attack sites in vivo is limited by the turnover and repair events. Reductive radical stress has been less widely investigated than oxidative radical stress and both reaction conditions offer a wide scenario including all the possible amino acid mutations to be addressed by appropriate analytical tools. In this context we performed a complete characterization of Human Serum Albumin (HSA) damaged by reductive reactive species. HSA is a globular protein that accounts for over 50% of total plasma protein and has many functions (i.e. from ligand-binding and to antioxidant functions). It contains 6 Met residues and 35 Cys residues that form the 17 disulfide bridges, contributing to overall tertiary structure, and leaving one free. Combined Raman spectroscopy and MS experiments identified the whole set of modifications affecting Met and Cys residues. Gamma-irradiation was used to simulate the endogenous formation of reductive species. Scheme 1. Desulfurization of Met and Disulfide Bridges Residues by Reductive Radical Stress The damage under reductive radical conditions, such as in the presence of solvated electrons (eaq-) and Ho atoms, produces the modification of Met to alpha-aminobutyric acid (Aba), that is an amino acid not genetically coded, and the modification of Cys to Ala (Scheme 1). This reactivity was placed in a biomimetic context, analogously to other proteins.1,2 Indeed, the protein damage occurs with the parallel formation of thiyl radicals originated from Met and Cys/cystine residues (Scheme 1). CH3So and So- radicals are able to migrate from the aqueous to the membrane compartment and cause damage to unsaturated lipids by effecting the cis-trans geometrical isomerization of the lipid double bonds.
Desulfurisation reactions in human serum albumin associated with the formation of trans lipids in a mimetic model of biological membranes
A Torreggiani;AMSalzano;C Ferreri;C Chatgilialoglu
2010
Abstract
Post-translational mutation of sulfur-containing amino acid in the protein sequence via radical damage is an interesting field of investigation, although the easiness to find out the attack sites in vivo is limited by the turnover and repair events. Reductive radical stress has been less widely investigated than oxidative radical stress and both reaction conditions offer a wide scenario including all the possible amino acid mutations to be addressed by appropriate analytical tools. In this context we performed a complete characterization of Human Serum Albumin (HSA) damaged by reductive reactive species. HSA is a globular protein that accounts for over 50% of total plasma protein and has many functions (i.e. from ligand-binding and to antioxidant functions). It contains 6 Met residues and 35 Cys residues that form the 17 disulfide bridges, contributing to overall tertiary structure, and leaving one free. Combined Raman spectroscopy and MS experiments identified the whole set of modifications affecting Met and Cys residues. Gamma-irradiation was used to simulate the endogenous formation of reductive species. Scheme 1. Desulfurization of Met and Disulfide Bridges Residues by Reductive Radical Stress The damage under reductive radical conditions, such as in the presence of solvated electrons (eaq-) and Ho atoms, produces the modification of Met to alpha-aminobutyric acid (Aba), that is an amino acid not genetically coded, and the modification of Cys to Ala (Scheme 1). This reactivity was placed in a biomimetic context, analogously to other proteins.1,2 Indeed, the protein damage occurs with the parallel formation of thiyl radicals originated from Met and Cys/cystine residues (Scheme 1). CH3So and So- radicals are able to migrate from the aqueous to the membrane compartment and cause damage to unsaturated lipids by effecting the cis-trans geometrical isomerization of the lipid double bonds.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
