SELENIUM DOUBLES UP IN PROTEINS

Abstract

THE FIRST REPORT of a selenium-selenium bond in naturally occurring proteins characterizes the linkage's low redox potential and suggests that it might play a role in regulation of redox levels in cells ( Proc. Natl. Acad. Sci. USA , DOI: 10.1073/ pnas.0703448104). The bond, described by a team led by biochemist Vadim Gladyshev at the University of Nebraska, unites two nearby selenocysteine residues in members of a protein family found mainly in aquatic animals and bacteria. Mass spectrometry sequencing verified the selenium-selenium bond and revealed a characteristic isotope signature of a compound containing two selenium atoms. The two linked selenocysteines are located in these proteins' active site and are organized in a manner reminiscent of the pair of catalytic cysteines found in the active site of thioredoxins. These proteins use a reversible disulfide bond to reduce cellular substrates. On the basis of this similarity, Gladyshev suggests that the new protein family may play a ...