A green fluorescent protein fusion strategy for monitoring the expression,cellular location, and separation of biologically active organophosphorus hydrolase

Organophosphorus hydrolase (OPH) is capable of degrading a variety of pesti cides and nerve agents. We have developed a versatile monitoring technique for detecting the amount of OPH during the expression and purification step s. This involves fusion of the gene for green fluorescent protein (GFP) to the 5' end of the OPH gene and subsequent expression in Escherichia coli. T he synthesized fusion protein was directly visualized due to the optical pr operties of GFP. Western blot analyses showed that the correct fusion prote in was expressed after IPTG-induction. Also, the in vivo GFP fluorescence i ntensity was proportional to the OPH enzyme activity. Moreover, the OPH, wh ich forms a dimer in its active state, retained activity while fused to GFP , Enterokinase digestion experiments showed that OPH was separated from the GFP reporter after purification via immobilized metal affinity chromatogra phy, which in turn was monitored by fluorescence. The strategy of linking G FP to OPH has enormous potential for improving enzyme production efficiency , as well as enhancing field use, as it can be monitored at low concentrati ons with inexpensive instrumentation based on detecting green fluorescence.