Metallothionein Protein Expression ofCrassostrea hongkongensisin Response to Cadmium Stress

Abstract

ABSTRACT Metallothioneins (MT) play important roles in trace metal homeostasis as well as excess metal detoxification in all organisms. They have been acknowledged as the most valid biomarker to indicate metal exposure in both vertebrates and invertebrates. In this study, the coding sequence of MT of a mollusk, the oyster Crassostrea hongkongensis, was determined by molecular cloning. The derived peptide sequence is composed of 75 amino acid residues of high cysteine content (28%). Blast analysis indicated that the MT gene in C. hongkongensis shares high homology with the MT genes of other aquatic invertebrates. The prokaryotically expressed ChMT protein was purified and used as antigen in the development of polyclonal antibodies, allowing the quantification of ChMT expression by competitive enzyme-linked immunosorbent assay in various tissues of the oyster on CdCl2-stressed conditions. Clear inductions of MT expression were observed in the digestive gland, gills as well as mantle by CdCl2 at a concentrat...