In vitro incorporation of selenomethionine into protein by Astragalus polysomes [Selenium toxicity]

Selenium-accumulator plants synthesize selenium compounds that differ from those produced by nonaccumulators. To determine if there are any subcellular differences between accumulators and nonaccumulators in the use of selenomethionine in vitro, polysomes from Astragalus crotalariae (accumulator) and Astragalus lentiginosis (nonaccumulator) were translated in the presence of selenomethionine. Polysomes from both species efficiently used selenomethionine in vitro during the translation process. Inasmuch as no differences in the incorporation of selenomethionine into protein were observed between polysomes from the two types of Astragalus, it can be inferred that in accumulators there exists a mechanism that either prevents synthesis of selenomethionine or modifies this selenocompound to a derivative that cannot be incorporated into protein.