Isolation and partial characterization of cadmium-induced metallothionein-like proteins in Mytilus galloprovincialis
Induced cadmium-binding proteins in Mytilus galloprovincialis were isolated from digestive gland and mantle edge tissue by conventional column liquid chromatography using gel-filtration (Sephadex G-75) and anionic-exchange (diethylamino ethyl-cellulose) techniques. Isolated protein fractions were co...
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Veröffentlicht in: | Marine chemistry 1991-12, Vol.36 (1), p.249-265 |
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Zusammenfassung: | Induced cadmium-binding proteins in
Mytilus galloprovincialis were isolated from digestive gland and mantle edge tissue by conventional column liquid chromatography using gel-filtration (Sephadex G-75) and anionic-exchange (diethylamino ethyl-cellulose) techniques.
Isolated protein fractions were considered to be metallothionein-like proteins (MLPs) due to their high cadmium and sulphydryl content, as well as their chromatographic behaviour and spectral characteristics. Two negatively charged MLP components (MLP-I and MLP-II) were separated from digestive gland, both possessing a molar mass of 12.6 kDa as determined by electrophoresis. The electrophoretic profile of mantle edge MLP showed another strongly pronounced band of 26 kDa in addition to one at 12.6 kDa, indicating the occurrence of a predominantly dimeric form in that tissue.
The sulphydryl to cadmium ratio, determined by electrochemical and spectrophotometric methods, in addition to flameless atomic absorption spectrophotometry (AAS), was in the range between 2.1 and 2.5 in the highly purified, electrophoretically homogeneous MLP-II component from the digestive gland of
M. galloprovincialis. This is considerably lower than the well-defined binding stoichiometry of mammalian type metallothionen.
This observed lower cysteine to cadmium ratio may conceivably be related to a specific coordination geometry, presumably implicating mixed ligand complexation of metal-binding sites in MLPs of
M. galloprovincialis. |
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ISSN: | 0304-4203 1872-7581 |
DOI: | 10.1016/S0304-4203(09)90065-2 |