Metallothioneins (MTs) are low molecular weight, cysteine-rich, metal-binding proteins. MTs are thought to be involved in the cellular detoxification of metals (e.g., Cd and Hg) and homeostasis of essential metal ions (e.g., Zn and Cu) in mammals. However, little is known about the functions of MT in bivalveTegillarca granosa () using RT-PCR. The open reading frame (ORF) of TgMT was 234 bp encoding a polypeptide of 77 amino acids with a predicted molecular mass of 7.9 kD. Phylogenetic analysis suggested that TgMT was most closely related to MT from . We constructed a recombinant expression plasmid (pET32a-MT) by inserting the TgMT ORF into the prokaryotic expression vector pET-32a. The recombinant TgMT was successfully expressed in BL21 (DE3) following induction with IPTG. SDS-PAGE analysis confirmed the expression of TgMT, which had a molecular mass of about 28.3 kD, in agreement with the expected molecular weight. The recombinant protein was primarily expressed as a soluble protein and was purified by Ni-NTA His-Bind Resin. We injected the purified TgMT into rabbits to obtain polyclonal antiserum against TgMT for use in immunoblotting experiments. Real time PCR and western blot analysis revealed that TgMT was distributed ubiquitously in a range of tissues. Expression was highest in the digestive glands of . We performed immunohistochemistry using a laser confocal microscope to examine the cell distribution of TgMT in the digestive gland. TgMT was primarily localized in the cytoplast of the digestive tubule epithelium. Our results provide insight into the utility of using MT proteins for environmental monitoring and into the mechanisms controlling detoxification in