Improving the soluble expression of aequorin in Escherichia coli using the chaperone-based approach by co-expression with artemin.

Escherichia coli is a common host that is widely used for producing recombinant proteins. However, it is a simple approach for production of heterologous proteins; the major drawbacks in using this organism include incorrect protein folding and formation of disordered aggregated proteins as inclusion bodies. Co-expression of target proteins with certain molecular chaperones is a rational approach for this problem. Aequorin is a calcium-activated photoprotein that is often prone to form insoluble inclusion bodies when overexpressed in E. coli cells resulting in low active yields. Therefore, in the present research, our main aim is to increase the soluble yield of aequorin as a model protein and minimize its inclusion body content in the bacterial cells. We have applied the chaperone-assisted protein folding strategy for enhancing the yield of properly folded protein with the assistance of artemin as an efficient molecular chaperone. The results here indicated that the content of the soluble form of aequorin was increased when it was co-expressed with artemin. Moreover, in the co-expressing cells, the bioluminescence activity was higher than the control sample. We presume that this method might be a potential tool to promote the solubility of other aggregation-prone proteins in bacterial cells.