[Recombinant colorimetric antibodies: genetic construction and production in E. coli].

We constructed an expression vector comprising a transcription unit composed of (1) the gene of alkaline phosphatase from E. coli in which we inserted a DNA fragment encoding the VH and CH domains of an IgG2A; (2) a DNA fragment encoding the light chain of the same immunoglobulin. Bacteria, E. coli were transformed with the plasmid, and hence it produced a periplasmic and chimaeric protein having both the alkaline phosphatase enzymatic activity and the immunoglobulin binding function. The hybrid protein mimics a bivalent antibody whose Fc part is replaced by a dimer of alkaline phosphatase. Recombinant colorimetric antibodies offer interesting potentialities for future developments in the field of immuno-enzymatic diagnosis.