title: On the mechanism of selenium tolerance in selenium-accumulating plants. Purification and characterization of a specific selenocysteine methyltransferase from cultured cells of Astragalus bisculatus.
abstract: Selected members of the genus Astragalus (Fabaceae) are known for their ability to accumulate high levels of selenium, mainly in the form of Se-methyl-selenocysteine. With the aid of cell cultures we have investigated the molecular basis for selenium tolerance of these plants. It is shown that cultured cells from a selenium-accumulating Astragalus species synthesize Se-methyl-selenocysteine in contrast to those of a non-accumulating species and do not unspecifically incorporate selenium into proteins. The purification and biochemical characterization of a selenocysteine methyltransferase from cultured Astragalus bisculatus cells is described, which does not accept cysteine as a substrate. We propose that this enzyme plays a crucial role in conferring selenium tolerance.
authors.affiliation: Institut für Genetik und Mikrobiologie, München, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Neuhierl
authors.forename: A
authors.initials: A
authors.lastname: Böck
mesh_terms: D000222:Adaptation, Physiological; D002478:Cells, Cultured; D008658:Inactivation, Metabolic; D008780:Methyltransferases / Q000378:metabolism*; D018521:Plant Physiological Phenomena; D010944:Plants / Q000201:enzymology / Q000378:metabolism*; D012643:Selenium / Q000378:metabolism* / Q000493:pharmacokinetics; D013379:Substrate Specificity
chemical_list: D008780:Methyltransferases; C100751:selenocysteine methyltransferase; D012643:Selenium