Expression of codon-optimized TgMIC16 in three Escherichia coli strains.

In a previous study, we found that rabbit anti-Toxoplasma gondii serum was capable of recognizing truncated T. gondii microneme protein 16 (TgMIC16), indicating that TgMIC16 is an essential antigenic T. gondii protein. However, the broad application of this recombinant protein is limited by its low expression level. In this study, we performed codon optimization of TgMIC16 by changing the codon-adaptation index from 0.22 to 1.0 without altering the amino acid sequence and expressed the optimized gene in three different Escherichia coli strains, followed by comparison of soluble recombinant-protein expression and yield. Our results showed that the recombinant protein rTgMIC16 was expressed as inclusion bodies in all three strains following optimization of induction parameters, and western blot analysis revealed the presence of a ~72-kD recombinant protein as a specific band following purification. A shuffle-expression strain was selected to amplify incubation products and induce expression, resulting in an overall rTgMIC16 yield of ~20 mg/L. These findings provide a basis for further investigation of TgMIC16 to elucidate its functions and interaction partners.