Determining heterogeneity in purified recombinant proteins

Abstract

Proteins are biomolecules that are essential for life and often serve as targets for antimicrobial drugs. During antimicrobial drug design and development, it is common to use a recombinant version of the protein target to assess the efficacy of the compound. However, during expression, heterogeneity in the protein’s structure/sequence can occur. This can result in reduced purity and long-term stability of the protein and thus, it is imperative that the extent of heterogeneity of the proteins used for drug development is addressed. In our project, we assessed the heterogeneity of recombinant Y. pestis DXP reductoisomerase (DXR, IspC). In doing so, we first expressed, harvested, and purified the recombinant protein which was subsequently evaluated using SDS-PAGE. The resulting purified protein was then trypsinized by incubating the protein with the enzyme trypsin at various concentrations and durations and the resulting fragments were visualized using SDS-PAGE. Finally, we compared our digested protein to a theoretical in-silico-derived digest, permitting us to determine the extent of heterogeneity within our recombinant protein.