Characterization of metallothionein‐like proteins from zebra mussels (Dreissena polymorpha)

Abstract

Abstract-Zebra mussels (Dreissena polymorpha) are freshwater mollusks that have recently infested the Great Lakes ecosystem. Possessing a large capacity for filtration, these mussel populations act as bioconcentrators for contaminants, such as heavy metals, found in the Great Lakes ecosystem. Metallothionein is a low-molecular-weight, heavy metal-binding protein found in most living organisms. Characterization and partial purification of metallothionein-like Cd-binding proteins from zebra mussels were performed. Zebra mussels were exposed to 500 g/L Cd for 14 d. During the exposure period, two mussels were removed on alternate days for analysis of Cd-binding proteins. Gel-filtration high-performance liquid chromatography-microatomization-atomic absorption spectrophotometry results showed a single Cd-binding molecular weight protein fraction after 2 d of Cd exposure. After 10 d of Cd exposure, however, mussels exhibited an additional, higher molecular weight, Cd-binding protein fraction. The lower molecular weight metallothionein-like Cd-binding protein was further isolated and purified by acetone fractionation, Sephadex G75, and diethylaminoethyl anion-exchange chromatography. The quantities of Zn, Cu, and Cd in the anion-exchange metallothionein-like protein isoforms were determined by inductively coupled plasma-mass spectrometry. The ability to bioconcentrate heavy metals in a metallothionein-like form coupled with their large population in the Great Lakes make zebra mussels suitable for use in a freshwater biomonitoring program for aquatic metal contamination.

Improved separation of rabbit liver metallothioneins by FPLC-ICP-MS: a comparison with the conventional anion-exchange chromatography

“…Our results are similar to those previously found in Zebra mussels by High et al who used a TSK-Gel DEAE 5PW, a conventional anion-exchange column, except that in their work MLP-1 and MLP-2 isoforms were found to appear at retention times longer than 30 min [20].…”

Metallothionein-2 gene from the mandarin fish Siniperca chuatsi: cDNA cloning, tissue expression, and immunohistochemical localization

“…However, more possible reason might be that the retarded migration caused by the status of MTs binding metal ions (Chyan et al, 2005). The similar molecular weight of MT-like proteins also have been reported in other fish, e.g., the channel catfish (Ictalurus punctatus) (Chatterjee and Maiti, 1987), killfish (Heterandria formosa) (Xie and Klerks, 2004) and the mollusk, for example, the zebra mussel (Dressena polymorpha) (High et al, 1997). Different expressions patterns between the level of mRNA and the level of protein were observed in present study, and these may not be mutually exclusive.…”

Cellular and subcellular distribution of metals in molluscs

“…Sulfur donors, such as MT and other metal-binding proteins, have been found in digestive cells of the digestive diverticula, podocytes, and nephrocytes, as well as in migrating hemocytes and phagocytes (named pore cells or brown cells, depending on the species), where metals such as Cd, Cu, and Fe (class "b" and some borderlines) are accumulated in lysosomes Mason et al, 1984;Marigómez et al, 1990aMarigómez et al, , 1995Janssen and Dallinger, 1991;Bebianno and Langston, 1992;Carpene, 1993;Rubio et al, 1993;Soto et al, 1996a,b;Baudrimont et al, 1997;High et al, 1997).…”