Synergistic interaction between lac and uspA promoters’ expression systems for recombinant protein production in Escherichia coli

Recombinant proteins need to be produced on a large-scale, short time and at a low cost. Different elements need to be controlled to achieve these characteristics. One of the most relevant is the promoter sequence since it is responsible for initiating the transcription process. Several promoters are already commercially used, but none is suitable for high-scale protein production due to the cost of the induction method, the leaky expression, the limited media options, etc. Furthermore, most current expression systems rely on the single use of a promoter to control the gene transcription. At the same time, in nature, this is not always the case since there are tandem promoters’ arraignments in control of a single gene. Using tandem promoters is an attractive idea to enhance the recombinant protein production considering that this significate the incorporation of more sites where the RNAP-complex could bind, enhancing recombinant protein production this way. Based on this, a triple-promoter expression system was developed in Escherichia coli to improve the yields of the red fluorescent recombinant protein (mRFP1). Two copies of the well-known and established lac promoter were used, and the sequence of the uspA promoter, which is the promoter of the most abundant protein in Escherichia coli according to the Protein Abundance Database PAXdb4.1, were used in this system. Additionally, the uspA promoter can be induced by several stress conditions. Thus, it was tested under oxidative starvation. Results indicated a 0.82 FU µg-1 mL-1 and 0.8 FU µg-1 mL yields of the mRFP1 when using the triple-promoter expression systems compared to a 0.59 FU µg-1 mL-1 of the single-promoter expression system. Thus, indicating an enhancement in the production yields of the target protein. These results are promising and open an opportunity for further research in the multiple-promoter system.