Use of proZZ-obelin fusion protein in bioluminescent immunoassay.

Obelin is a photoprotein that emits light by Ca2+-binding. To develop a bioluminescent immunoassay based on the light emission property of obelin, we have expressed the apoobelin fusion protein with ZZ-domain of S. aureus protein A in E. coli by recombinant DNA techniques. The proZZ-obelin expressed was purified by one-step affinity chromatography on IgG-Agarose. The purified proZZ-obelin has both the luminescent activity of obelin and the IgG-binding ability of ZZ-domain. The specific activity of fusion protein was 8.5 X 10(15) photons per mg of protein.