Evaluating Heterogeneity of Recombinant Protein Expression

Abstract

Drug development often employs the use of recombinant proteins to produce vaccines, treat cancers, and develop antibiotics. However, heterogeneity in the protein’s structure can occur, confounding experimental results which can lead to inaccuracies in data acquisition and interpretation. Thus, assessing and minimizing the extent of heterogeneity during expression and purification of recombinant proteins is crucial. In our project, we assessed the heterogeneity of purified recombinant F. tularensis DXP reductoisomerase (DXR, IspC), an enzyme found within the MEP pathway. To do so, we first expressed and harvested an engineered E. coli strain which contained our recombinant protein of interest. The protein was subsequently purified using column chromatography and the results evaluated by SDS-PAGE. Next, our protein was trypsinized resulting in a fragmentation pattern unique to our recombinant F. tularensis IspC. Finally, by using in-silico trypsinization, we compared our results to a theoretical digest, enabling us to determine the extent of heterogeneity within our recombinant protein.