Difference between revisions of "Part:BBa K346085"

        The intensity of T7 RNA polymerase (T7 RNAP) expression is essential to the production of the target gene on pET plasmid. In BL21 (DE3), the gene encoding the T7 RNAP is under control of the strong lacUV5 promoter (PlacUV5), which is leakier and strong. These characteristics are not advantageous for the production of those recombinant proteins with toxic or growth-burdened. While our project was focused on the translational level of T7 RNAP, we were also paying attention to the transcription level of T7 RNAP.

      In the composite part of(BBa_K346085), T7 RNAP was expressed under the Ptet, which was registered in 2010. Here, the composite part of(BBa_K346085)was inserted into the genome of BL21 (DE3) (Fig. 2A), yielding the strain of BL21 (DE3)-tet. We used the pET-eGFP plasmid to characterize the leakage ability of the Ptet and the transcription level of T7 RNAP. When addition of the inducer of anhydrotetracycline (aTc), the BL21 (DE3)-tet strain exhibited brighter fluorescent (Fig. 2A), indicating that the composite part of (BBa_K346085) can work in the BL21 (DE3). As shown in Fig. 2B, under the condition of no inducer, it can be seen that the Ptet exhibited the lowest leakage ability compared to that of the PlacUV5.

        Furthermore, the capacity of(BBa_K346085)for the production of recombinant proteins was investigated. As the proof of concept, the two membrane proteins of Ecb and Yidc were produced in BL21 (DE3)-tet, and the different concentration of aTc (0.6 μM, 2.4 μM, 7.0 μM) were performed, respectively (Fig. 2C). The production of Ecb was maximum when aTc concentration was 2.4 μM, which is 371.0 % and 44.6% higher than that of 0 uM and 7.0 μM, respectively. The production of Yidc in strain BL21 (DE3::tet) was optimized when aTc concentration was 7.0 μM, which is 17.0% higher than that of 2.4 uM. This results indicated that the production of the membrane proteins can be improved by(BBa_K346085). These results provide effective guide for future iGEM team to improve the production of hard-to-express proteins.

Fig.1 A. The fluorescence diagram of BL21 (DE3)-tet with or without inducer. B. Fluorescence intensity of different strains containing pET-eGFP plasmid. C. The expression of Ecb and Yidc under different inducer concentrations at 36 h.