Metallothioneins (MTs) are low molecular weight, cysteine-rich proteins with an exceptional heavy metal coordination capacity. Because of their ability to bind metals and to scavenge oxidant radicals, MTs are considered to play a role in metal homeostasis, metal detoxification and control of the oxidative stress.1 Although their high heterogeneity on the expression patterns, metal binding abilities and primary structure suggest very diverse functional specializations, the structural and functional studies have been mainly devoted to vertebrate and fungal MTs. Participation of metal ligands other than the cysteines and the presence of secondary structure elements in metal-MT complexes are fairly unknown, especially in non-vertebrate MTs. Recently, it has been shown that ligands other than Cys can participate in the coordination sphere of metals in MTs. Two main types have been identified: endogenous ligands such as imidazole moiety of His residues2 and /or exogenous ligands such as inorganic ions (i.e. sulfide or chloride ions).3 Six in vivo-synthesized Zn-complexed MTs representative of different MT families (mollusc, insect, nematode, echinoderm, vertebrate and plant), enclosing the well-known mammalian MT1 isoform, were studied by analytic and spectroscopic techniques. In particular, Raman spectroscopy is shown to be highly informative, providing information about the state of the cysteine sulfur atoms (metal coordinated and oxidised), the participation of histidine in metal coordination, and the molecular environment of tyrosine residues. These MT polypeptides (CeMT2, MeMT, SpMTA, MtnB, QsMT and the paradigmatic mouse MT1) contain from 43 to 73 amino acids, with at least 30% being Cys. Almost all the MTs considered are completely devoid of aromatic residues (Phe is present in SpMTA and QsMT, Tyr in CeMT2, and His in CeMT2and QsMT). The Zn(II)-MT complexes were heterologously synthesized in E.coli,4 in order to obtain aggregates representative of those formed in biological systems.
Metal-Metallothionein complexes: insights into structural features by Raman spectroscopy
A Torreggiani;
2008
Abstract
Metallothioneins (MTs) are low molecular weight, cysteine-rich proteins with an exceptional heavy metal coordination capacity. Because of their ability to bind metals and to scavenge oxidant radicals, MTs are considered to play a role in metal homeostasis, metal detoxification and control of the oxidative stress.1 Although their high heterogeneity on the expression patterns, metal binding abilities and primary structure suggest very diverse functional specializations, the structural and functional studies have been mainly devoted to vertebrate and fungal MTs. Participation of metal ligands other than the cysteines and the presence of secondary structure elements in metal-MT complexes are fairly unknown, especially in non-vertebrate MTs. Recently, it has been shown that ligands other than Cys can participate in the coordination sphere of metals in MTs. Two main types have been identified: endogenous ligands such as imidazole moiety of His residues2 and /or exogenous ligands such as inorganic ions (i.e. sulfide or chloride ions).3 Six in vivo-synthesized Zn-complexed MTs representative of different MT families (mollusc, insect, nematode, echinoderm, vertebrate and plant), enclosing the well-known mammalian MT1 isoform, were studied by analytic and spectroscopic techniques. In particular, Raman spectroscopy is shown to be highly informative, providing information about the state of the cysteine sulfur atoms (metal coordinated and oxidised), the participation of histidine in metal coordination, and the molecular environment of tyrosine residues. These MT polypeptides (CeMT2, MeMT, SpMTA, MtnB, QsMT and the paradigmatic mouse MT1) contain from 43 to 73 amino acids, with at least 30% being Cys. Almost all the MTs considered are completely devoid of aromatic residues (Phe is present in SpMTA and QsMT, Tyr in CeMT2, and His in CeMT2and QsMT). The Zn(II)-MT complexes were heterologously synthesized in E.coli,4 in order to obtain aggregates representative of those formed in biological systems.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
