GREEN FLUORESCENT PROTEIN AS A REAL-TIME QUANTITATIVE REPORTER OF HETEROLOGOUS PROTEIN-PRODUCTION

Since its cloning and commercial availability, applications of green f luorescent protein (GFP) as a reporter gene have become prevalent in m any aspects of science. The attributes of GFP could also be applied to the area of heterologous protein production. The work described here represents the first experiments to use GFP as a generic tool to monit or protein production in bioprocess development. We have constructed a plasmid containing an operon fusion of the two reporter genes GFP and chloramphenicol acetyl transferase (CAT). CAT served as a ''model'' r ecombinant protein product to demonstrate the in situ quantifiable rep orting mechanism of GFP. Our results indicate there is a direct correl ation between the fluorescence intensity of GFP and the functional act ivity of the downstream CAT protein. In;addition, there is a quantitat ive relationship between the level of CAT protein concentration and GF P fluorescence. These experiments provide the groundwork for using GFP as an in situ reporter gene for scale-up and process optimization of recombinant protein production.