Enzyme-complemented activatorsorbent assay (ECASA): Genetic engineering for enzyme-linked immunosorbent assay-type mercuric ion detection

The sensor component of bacterial mercury resistance systems is the metalloregulatory protein MerR, which has nanomolar sensitivity and high selectivity for Hg(II). A fusion protein of MerR and the alpha-peptide part of beta-galactosidase (LacZ alpha) was constructed by fusing the relevant genes. The protein exhibited both MerR functions and alpha-complementing activity to the inactive LacZ Delta M15 (M15) protein. The bifunctional character of the appropriate MerR-LacZ alpha-complemented M15 protein (MerR-LacZ alpha:M15 protein complex) was used to develop a Hg(II)-specific enzyme-complemented activatorsorbent assay. Hg(II) was immobilized and presented on a matrix taking advantage of the high affinity of Hg(II) to SH residues. The immobilized Hg(II) could be specifically detected down to the parts-per-billion level by quantifying the beta-galactosidase activity of the bound fusion protein complex. (C) 1998 Academic Press.