Abstract:

The metallothioneins (MT) in Boettcherisca peregrina larvae were induced and produced after their feeding on the dietary containing 800 μg cadmium chlorides per gram diet for 48 hours. Two forms of MTs (MT-Ⅰ and MT-Ⅱ) were isolated and purified from the supernatant of the whole body homogenates from the larvae after exposure to cadmium chlorides, using gel chromatography on Sephadex G-50, ion-exchange chromatography on UNO^TM Q1, and desalination on Bio-Gel P-6. Molecular weight for both MT-Ⅰ and MT-Ⅱ was 9 kD. Both MT-Ⅰ and MT-Ⅱ contained 7 cadmium atoms and 20 sulfhydryl groups per molecule, and showed the spectral characteristic of cadmium-thionein, i.e. a broad shoulder at 254 nm. As to amino acid composition, the content of cysteine residues was the highest, accounting for 36.6% and 31.8% of all amino acids for MT-Ⅰ and MT-Ⅱ respectively; however, the contents of aromatic amino acid and histidine were very low, just sharing 1%－2% of all amino acids.

Key words: Boettcherisca peregrine, metallothionein, isolation and purification, characterization analysis, amino acid composition