Cadmium-binding polypeptides in microalgal strains with laboratory-induced cadmium tolerance

Stralns of 5 algal specles that have been induced to develop tolerance to prev~ously toxic cadmium (Cd) concentrations were lnvestlgated for product~on of the Cd-binding polypepbdes, poly(y-glutamylcyste~nyl)glycines, (y-ECInG. Llquld chromatography uslng Sephadex G-50, ICP analysis of Cd ln chromatographic fracbons, and ammo acld analysis provided clear evidence of (y-ECInG producbon ln the 2 most tolerant species, Phaeodactylum tricornutum and Dunaliella terbolecta. Production of Cdbmdmg pepbde ln P. tricornutum was positively correlated with cellular Cd content, on a dry-weight basis. In contrastc Cd-tolerant strains of Isochrysis qalbana, Pavlova lutheri, and Tetraselmis maculata did not produce detectable (Y-EC)~G. Although Cd-tolerant I. gdbana differed from the control strain in some aspects of polypepbde content, as seen by the producbon of thiol-rich compounds, the speclflc mechanism for enhanced Cd tolerance ln the 3 species that do not produce (y-ECInG remams unknown,