Co-expression of chaperones for improvement of soluble expression and purification of an anti-HER2 scFv in Escherichia coli

Single‑chain fragment variable (scFv) is one of the most commonly used antibody fragments. They offer some advantages over full‑length antibodies, including better penetration to target tissues. However, their functional production has been a challenge for manufacturers due to the potential misfolding and formation of inclusion bodies. Here we evaluated the soluble expression and purification of molecular chaperone co‑expression.

E. coli BL21(DE3) cells were co‑transformed with the mixture of plasmids pKJE7 and pET22b‑scFv by the electroporation method. First, L‑arabinose was added to induce the expression of molecular chaperones, and then IPTG was used as an inducer to start the expression of anti‑HER2 scFv. The effect of cultivation temperature and IPTG concentration on soluble expression of the protein with or without chaperones was evaluated. The soluble expressed protein was subjected to native purification using the Ni‑NTA affinity column.

SDS‑PAGE analysis confirmed the successful co‑expression of anti‑HER2‑scFv and DnaK/DnaJ/GrpE chaperones. Co‑expression with chaperones and low‑temperature cultivation synergistically improved the soluble expression of anti‑HER2 scFv. Co‑expression with chaperone also exhibited an approximately four‑fold increase in the final yield of purified soluble protein.

The combination of co‑expression with chaperones and low temperature presented in this work may be useful for the improvement of commercial production of other scFvs in E. coli as functionally bioactive and soluble form.