(599aj) Elastin-like Polypeptide Tag Length Effect on Protein Expression and Purification

Recombinant protein technology has enabled the expression of fusion proteins that can be purified in bacterial systems with the use of purification tags. In particular, the elastin-like polypeptide (ELP) precipitation tag in the presence of a self-cleaving intein protein domain allows non-chromatographic purification of a target protein with only a change in salt concentration and pH. Shortening the ELP tag length has the potential to increase expression by freeing the energy that would be required to synthesize the large ELP repetitive protein sequence.  An increase in production yield of a given protein would thus be expected when decreasing the ELP tag length. Furthermore, the optimal ELP tag length needed may be affected by the size and solubility of the protein product fused with the tag. In this study, we will present our most recent work in discerning the effect of five different ELP tag sizes in the product yield of the expression and purification of the following model target proteins: β-galactosidase, β-lactamase, and enhanced green fluorescence protein. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) qualitatively suggests the success of each purification. The corresponding activity and Bradford assays will be used to confirm these results quantitatively.  The relationship between the target protein fused to the ELP-intein system and the ELP tag length required for its successful purification will be discussed.