FACTORS CONTROLLING SYNTHESIS OF A BACTERIAL SELENOPROTEIN

Abstract Organisms from bacteria to mammals contain a highly discriminatory system for insertion of selenium into polypeptides. Elucidation of the mechanisms governing this system could illuminate various aspects of gene expression and metabolism. The bacterium Escherichia coli produces two selenium-dependent formate dehydrogenase enzymes under anaerobic conditions. They are expressed alternatively in the presence (FDHN) or absence (FDHN) of nitrate. Factors controlling the synthesis of FDHH were studied using fusions of the FDHH gene with the beta-galactosidase structural gene. Unlike other anaerobically-expressed proteins, inhibitors of DNA supercoiling increase synthesis of the gene product. An in vitro system for coupled transcription and translation of the fusion gene has been analyzed to determine components essential for selenium incorporation into polypeptides.