ABSTRACT
ScFv is emerging as a therapeutic alternative to the full-length monoclonal antibodies due to its small size and low production cost, but its low solubility remains a limiting factor toward wider use. Here, we increased the solubility of an Anti-epidermal growth factor receptor ScFv (Anti-EGFR ScFv) by attaching, a short 12-residue solubility enhancing peptide (SEP) tag at its C terminus. We first estimated the solubility increase by running 500-ns Brownian dynamics (BD) simulations. We then experimentally evaluated the predictions by producing recombinant Anti-EGFR ScFv with and without a SEP tag (called C9R) in E. coli. At 20⯰C, â¼85% of Anti-EGFR ScFv-C9R expressed in the soluble fraction, whereas all of the Anti-EGFR ScFv remained in the insoluble fraction. The total yield of Anti-EGFR ScFv-C9R was 17.15â¯mg which was â¼3 times higher than that of Anti-EGFR ScFv refolded from the insoluble fraction. Static and dynamic light scattering demonstrated the higher solubility of the purified Anti-EGFR ScFv-C9R, and Circular Dichroism (CD) indicated its high thermal stability, whereas the untagged protein aggregated at 37⯰C and pH 6. Finally, the binding activity of Anti-EGFR ScFv-C9R to EGFR was confirmed by surface plasmon resonance (SPR). Altogether, these results illustrate the improved biophysical and biochemical characteristics of Anti-EGFR ScFv-C9R and emphasize the potentials of SEP-tags for enhancing the solubility of aggregation-prone antibody fragments.
Subject(s)
ErbB Receptors/immunology , Single-Chain Antibodies/immunology , Amino Acid Sequence , Dynamic Light Scattering , ErbB Receptors/chemistry , ErbB Receptors/isolation & purification , Mutant Proteins/genetics , Mutant Proteins/isolation & purification , Mutation/genetics , Protein Binding , Protein Structure, Secondary , Recombinant Proteins/chemistry , Single-Chain Antibodies/chemistry , Single-Chain Antibodies/isolation & purification , Solubility , Surface Plasmon ResonanceABSTRACT
Tobacco Etch Virus (TEV) protease is used in the purification of recombinant proteins, but its usage is often hampered by solubility issues. Here, we report a short, 12-residue solubility enhancing peptide (SEP) tag attached at the C-terminus of TEV (TEV-C9R). We assessed the effects of the C9R tag on the biophysical and biochemical characteristics of TEV. The yield of HPLC purified TEV-C9R expressed in E. coli grown in 200â¯mL LB or TB media was between 10 and 13â¯mg, which was up to 6.5 times higher than the yield of the untagged TEV (untagged-TEV). TEV-C9R was active over a pH range of 5-8, which was wider than that of the commonly used thrombin, and it remained active upon incubation at 60⯰C much longer than the untagged-TEV, which aggregated at this temperature. Static and dynamic light scattering demonstrated the higher solubility of purified TEV-C9R. Furthermore, the thermal unfolding of TEV-C9R, as assessed by circular dichroism at pH 4.7, was almost perfectly reversible, in contrast to that of untagged-TEV, which aggregated at high temperature. These results demonstrate the improved biophysical and biochemical characteristics of TEV-C9R originating from higher solubility and provide another example of how SEP tags can enhance enzyme solubility without altering its activity.