Isolation and Characterization of Cadmium Metallothionein Gene from Local Ciliates

Abstract

First cadmium metallothionein like gene PMCd1 of a ciliate, Paramecium sp., isolated from indus- trial wastewater has been cloned and sequenced. PMCd1 is an intronless gene, encoding 612 nucleotides, with TAA coding for glutamine. The coding region of PMCd1 com- prises 203 amino acids, including 37 cysteine residues with a conserved structural pattern in the form of recurring structural motifs, arranged in 17 x-cys-x-y-cys-x, 1 x-cys- cys-x and x-cys-x contexts. Both, the deduced amino acids and nucleotide sequence differ, not only from other animal metallothioneins (MTs), but also from the previously characterized Tetrahymena Cu and Cd-MTs. The translated protein of PMCd1 contains conserved cysteine residues, peculiar characteristic of stress inducible metallothionein genes of ciliates and other groups of organisms.