The role of metal-sulfur clusters in the cis-trans isomerization of unsaturated fatty acids

Using biomimetic models of proteoliposomes, a tandem protein-lipid damage process has been suggested to occur from the initial free radical damage of sulfur-containing proteins/peptides, causing the release of diffusible species, which in their turn are able to effect a second damage by isomerization of membrane lipids.1,2 The model mimicked the tandem damage involving two biological compartments, the cell membrane and the soluble protein domain. Metallothioneins (MTs) are a unique class of low-molecular weight metalloproteins,3 which have different arrangements of metal-thiolate clusters, including cysteine or histidine residues and inorganic sulfur moieties. Non-enzymatic modifications of MTs (forming metal complexes with Zn(II), Cd(II) or Cu (I) ions) have been studied using ionizing radiations as free radical initiation, and analyzing the protein structural transformations by Raman spectroscopy. In the biomimetic model the trans unsaturated fatty acid content has been evaluated as result of radical stress on MTs.3,4