Metallothioneins are typically low relative molecular mass (6000–7000), sulfhydryl-rich metal-binding proteins with characteristic repeating cysteine motifs (Cys-X-Cys or Cys-Xn-Cys) and a prolate ellipsoid shape containing single a-andb-domains. While functionally diverse, they play important roles in the homeostasis, detoxification and stress response of metals. The originally reported metallothionein of the American oyster,Crassostrea virginicashowed the canonical molluscanab-domain structure. .
