Difference between revisions of "Part:BBa K3168004"

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dCas9-LargeBitNanoLuc

This composite part is made up of two basic parts (figure 1). The first basic part (BBa_K3168000) codes for a catalytically dead CRISPR associated protein 9 (dCas9). dCas9 binds to a specific double-stranded DNA sequence which is determined by the guide RNA. The second basic part (BBa_K3168002), which is fused to dCas9, consists of a (GGS)₅ linker and the large bit of NanoLuc. When the large bit of Split-NanoLuc forms a complex with the small bit and the substrate Furimazine is present, blue light is emitted. dCas9-LargeBit itself is slightly bioluminescent when the substrate is added. However, the intensity is more bright when a complex is formed with the small bit. Thus this composite part is part of a Split-NanoLuc detection system, which targets a specific sequence on dsDNA and sends out a bioluminescent signal upon binding of this specific sequence (figure 2).

Figure 1. Schematic representation of dCas9-LargeBitNanoLuc.

Usage and Biology

dCas9 in combination with guide RNA forms a dsDNA recognition complex. A stronger bioluminescent signal is created when dCas9-LargBitNanoLuc and dCas9-SmallBitNanoLuc bind in close proximity.

Figure 2. Schematic representation of dCas9-Split-NanoLuc system.

Characterization

Expression
The fusion protein was successfully expressed in BL21(DE3) and purified with immobilized metal affinity chromatography (IMAC). The elution was collected in 5 fractions of 1.5 mL. The three elution samples with the highest concentrations were put on an SDS-PAGE gel to evaluate the purity and molecular weight of the samples. dCas9-LargeBitNanoLuc has a molecular weight of 178 kDa. As shown in figure 3, there are very obvious blobs of dCas9-LargeBitNanoLuc above 150 kDa. There are other bands visible so the purity is not optimal. However, the contrast between the huge blobs and the other bands is very big.

Figure 3. SDS-PAGE gel of IMAC elution samples of dCas9-LargeBitNanoLuc (Elute 2: 17.90 μM, Elute 3: 6.37 μM, Elute 4: 2.88 μM).

References

Dixon, A. S., Schwinn, M. K., Hall, M. P., Zimmerman, K., Otto, P., Lubben, T. H., ... & Wood, M. G. (2015). NanoLuc complementation reporter optimized for accurate measurement of protein interactions in cells. ACS chemical biology, 11(2), 400-408.

Zhang, Y., Qian, L., Wei, W., Wang, Y., Wang, B., Lin, P., ... & Cheng, S. (2016). Paired design of dCas9 as a systematic platform for the detection of featured nucleic acid sequences in pathogenic strains. ACS synthetic biology, 6(2), 211-216.

Sequence and Features