Selenophosphate — selenium donor for protein and tRNA

Monoselenophosphate has been identified as the activated selenium donor in Escherichia coli that is required for both the biosynthesis of selenocysteine in selenium-dependent enzymes and for the conversion of 2-thiouridine residues to 2-selenouridine in tRNA. Selenophosphate is generated from ATP and selenide by the selD gene product, selenophosphate synthetase.