Part:BBa_K4854025

CsgA+zig-4

This composite part contains lac promoter(BBa_R0010)^[1], RBS(BBa_B0034)^[2], CsgA(BBa_K4854013)^[3], GS linker(BBa_K4854012)^[4] and zig-4(BBa_K4854011)^[5] gene. It is meant to express a fusion protein of the E. coli membrane protein CsgA and Zwei Ig domain protein zig-4.
Zwei Ig domain protein zig-4 from the roundworm (Caenorhabditis elegans) plays a role in maintaining axon position.^[6]
CsgA protein is the major component of biofilms of E. coli. It can self-assemble into a network of amyloid nanofibers outside the cell. Because of this characteristic, CsgA can be a platform to display recombinant protein on the surface of E. coli.^[7]
We performed codon optimization to improve gene expression in E. coli.

Figure 1. The circuit of the CsgA+zig-4 protein.

Cloning result

We successfully inserted CsgA+zig-4 gene into pSB1A3 plasmid and amplified it in E. coli DH5α. After DNA sequencing, we replaced the vector pSB1A3 with pSB3K3 for better protein expression. Then the plasmid was transformed into E. coli C41 for protein expression.

Figure 2. Gel electrophoresis result.

Functional test

After expressed in E. coli C41 by 200 μM IPTG for 12 h at 37 ℃, we performed flushing test, viscosity test by rheometer, and modified ELISA to check whether CsgA+zig-4 protein has adhesive properties.

1. Flushing test
With the flushing test, we can determine whether the functional adhesive recombinant protein was adhesive initially. We used our backbone pSB3K3+J04450 as control. From Figure 3, we could make a preliminary decision that CsgA+zig-4 had obvious adhesion to stick on the slides.

Figure 3. Flushing test results.

2. Viscosity test
In Prof. Ming-Chia, Lee's lab, we used rheometer to further test the viscosity of functional adhesive recombinant protein. Taking the percentage of the viscosity of CsgA+zig-4 divided by the viscosity of J04450 (control), CsgA+zig-4 was 314.15% higher. We could tell that it was highly adhesive.

Figure 4. The viscosity test results of potential adhesive recombinant proteins. The y-axis is the percentage of the viscosity of the potential adhesive recombinant proteins divided by the viscosity of J04450 (control).

3. Modified ELISA
With the principle of ELISA antibody and antigen binding, we designed the modified ELISA to test whether CsgA+zig-4 had a great ability to capture antibodies. We replaced the antigen with the produced protein, used the viscosity of protein to capture the antigen and determined the strength of the binding antibody signal by OD₆₃₀. We did a triple repeat and took the average value as the data. Based on Figure 5, the ability of capturing the antibodies of CsgA+zig-4 was 114.63% better than control (J04450). We could tell that the potential adhesive recombinant protein CsgA+zig-4 could capture antibodies effectively.

Figure 5. The modified ELISA test triple repeat OD₆₃₀ mean value of potential adhesive recombinant proteins. The y-axis is the percentage of the mean value of the potential adhesive recombinant protein OD₆₃₀ divided by the mean value of J04450 (control) OD₆₃₀.

Reference
[1] https://parts.igem.org/Part:BBa_R0010
[2] https://parts.igem.org/Part:BBa_B0034
[3] https://parts.igem.org/Part:BBa_K4854013
[4] https://parts.igem.org/Part:BBa_K4854012
[5] https://parts.igem.org/Part:BBa_K4854011
[6] https://www.uniprot.org/uniprotkb/G5ECB1/entry
[7] Fei Li, Luona Ye, Longyu Zhang, Xiaoyan Li, Xiaoxiao Liu, Jiarui Zhu, Huanhuan Li, Huimin Pang, Yunjun Yan, Li Xu, Min Yang, Jinyong Yan, Design of a genetically programmed barnacle-curli inspired living-cell bioadhesive, Materials Today Bio, Volume 14, 2022.

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  COMPATIBLE WITH RFC[1000]