Part:BBa_K4623009

Twisted Silinker,Silica-protein junctions that curving in response to calcium ions

Usage and Biology

Twisted Silinker (TS) is an intelligent recombinant protein that efficiently connects to the surface of silicon dioxide while undergoing conformational changes in response to environmental stimuli.

The sequence added a His-tag , allowing purification of Twisted Silinker protein using a nickel column. An upstream TrxA fusion tag (BBa_K3619001) is added to aid in protein folding and reduce the formation of inclusion bodies in the bacterial host. After protein expression. CBP (BBa_K3755007) and calmodulin (BBa_I757003) undergo conformational changes in the presence of calcium ions, tightly folding together to achieve the desired conformation. The SBP (BBa_K4623001) sequence can bind to the silicon dioxide surface, facilitating the modification of functional proteins onto the surface.

We transferred the pET-Duet1 plasmid into our engineered strain BL21 (DE3) and performed small-scale expression to determine the production conditions for His-tagged Twisted Silinker. The purified Twisted Silinker was detected using SDS-PAGE and Western Blot, with a molecular weight of 53kDa. To improve the purification strategy, we have also developed corresponding hardware for protein purification using the binding affinity between SBP and silicon dioxide, significantly enhancing the efficiency of protein production and purification. For reference, the hardware details can be found at our wiki.

Cultivation, Purification and SDS-PAGE

induction condition

To ensure proper folding of mSA and minimize inclusion body formation, we modified the protein buffer by adding biotin. The binding of biotin to mSA can help facilitate proper folding of the Twisted Silinker protein, reducing the formation of inclusion bodies resulting from misfolding. As a result, we obtained soluble protein extract in the supernatant. The formulation of the buffer and experimental procedures can be found in (protocol) for reference. We chose 0.1mM IPTG for induction, and the target protein concentration was in a high level, which was the effective induction concentration.

Figure 1 | Twisted Silinker Protein Purification SDS-PAGE gel. Massive expression of Twisted Silinker protein was performed under 16°C, 0.1mM IPTG induction, followed by nickel column affinity chromatography purification. A Blue Plus V Protein Marker (10-190kDa) was used for size comparison. Lane 1 represent the 500mM imidazole elution and Lane 2 represented the 500mM imidazole elution. The gel was stained with Coomassie brilliant blue and subjected to protein gel analysis.

Purification of Twisted Silinker

After successfully determining the expression conditions of Twisted Silinker protein, it is necessary to scale up the culture and proceed with purification. We induced expression with 0.1mM IPTG and allowed it to proceed at 16°C for 20 hours, resulting in a large amount of the target protein. In the process of constructing the expression vector, we incorporated a His-tag into the target protein and utilized a nickel column for affinity chromatography purification based on the specific binding of the His-tagged protein. As shown in Figure 2, the bands displayed successful elution of a significant amount of the target protein using 500mM imidazole solution.

Figure 2 | Twisted Silinker Protein Purification SDS-PAGE gel. Massive expression of Twisted Silinker protein was performed under 16°C, 0.1mM IPTG induction, followed by nickel column affinity chromatography purification. A Blue Plus V Protein Marker (10-190kDa) was used for size comparison. Lane 1 represent the 500mM imidazole elution and Lane 2 represented the 500mM imidazole elution. The gel was stained with Coomassie brilliant blue and subjected to protein gel analysis.