ISOLATION OF A METAL-BINDING PROTEIN FROM OVARIES OF DAB (LIMANDA-LIMANDA L) DISTINCT FROM METALLOTHIONEIN - EFFECT OF CADMIUM EXPOSURE

Metal-binding proteins were isolated from ovaries of dab (Limanda lima nda L.) caught in the North Sea, Separation of the heat-treated cytoso lic fraction of dab ovaries by gel-filtration chromatography revealed the presence of a major zinc-binding protein with a low-molecular-weig ht of 10,000-12.000 Da, similar to mammalian metallothionein (MT), The metal-binding protein was analyzed by anion-exchange chromatography a nd by reversed-phase high-performance liquid chromatography. The metal -binding protein from dab ovaries consists of one major isoform, Zinc could be displaced from the isoform by a saturation of the extract wit h cadmium, leading to altered retention of the protein at the RP colum n, In a laboratory experiment, dabs were treated intraperitoneally wit h cadmium (0.5 and 1.5 mg/kg body wt). In contrast to hepatic dab MT, the metal-binding protein in ovaries was not inducable by cadmium; how ever, dose-dependent amounts of cadmium were bound to the ovarian prot ein after the metal exposure, The amino acid composition was different from that of mammalian MT, The results suggest that the metal-binding protein in dab ovaries is possibly involved in ovary development and can be affected by cadmium exposure. (C) 1996 Academic Press, Inc.