Improvement of Liu iGEM 2017s part BBa_K2474000

With the use of site-direted mutagenesis we wanted to improve the part of last years LiU iGEM team (BBa_K2474000). This was done by removing the fusion protein and the unnecessary bases as shown in figure 1. By doing this the fluorescent protein mNeonGreen (mNG) can be used as a reporter in a fully functional operone, with the use of the AraC/pBAD inducible system. The two additions was made with site-directed mutagenesis. Firstly the stop codon was added and sequenced, which was later used as the new template for the mutation to add the SpeI site. As seen in figure 1, we used SpeI to cleave off the unnecessary bases from the plasmid, and later ligated it back together without the amyloid-beta 1-42 fragment.
As seen in figure 2, our mutated version had a higher intensity on a UV-table.

Figure 1. A illutration of the steps made.

Results

The results for our improved part can be seen in below. The reason we choose to improve this part was not only to create a functional reporter system, but also to illustrate the loss of exchange with a aggregation prone fusion tag. From fig 2. you can clearly see that the version without amyloid-beta 1-42 folds better and thus gives a much higher fluorescence, while the fusion version is having trouble. The two parts was grown in LB-medium, 0.25 mg/ml L-arabinose and 25 ug/ml chloramphenicol over 16 hours. They were then lysed through the "freeze-thaw" method and centrifuged. The supernatant was saved and placed on an UV table as seen in fig 2.

Figure 2. From left to right: Reference with only water, BBa_K2671000 (mutated part) and BBa_K2474000.

Sequencing

Figure 3. The chromatograms from sequencing. Left is BBa_K2671000 (mutated part) and right is BBa_K2474000 (template).