A recombinant DNA bio-assay for selenium in blood.

The trace element selenium (Se) is included in the form of selenocysteine (Sec) at the active site of several prokaryotic and eukaryotic proteins known as selenoproteins (SePro). The growing implications of SePro in cell physiology and human health point to the need for an adequate means of assessing Se status in biological fluids. Here, we describe a new approach based on a recombinant DNA construct, in which the expression of the 'lacZ gene in Escherichia coli is proportionally and specifically driven by UGA-directed Sec incorporation. Se status is determined in samples of rat blood first treated by acid hydrolysis for protein degradation. As compared to other methods, this simple, sensitive bioassay (BIO) for determining Se status seems to be unique in its ability to measure all functional Sec residues in SePro in blood serum.