Difference between revisions of "Part:BBa K5136035"

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inpnc-His tag-SpyCatcher

Biology

INPNC

Ice nucleoprotein (INP), an outer membrane protein from Pseudomonas syringae, has been used as a surface anchor in many researches. The truncated version of INP, namely INPNC which contains only the N- and C-terminal portion of INP, has excellent capacity to anchor target proteins on the cell membrane (1).

SpyCatcher

SpyCatcher is a engineered split fragment of the fibronectin-binding protein (FbaB) in Streptococcus pyogenes, containing 116 residues. SpyTag is a peptide tag of 13 residues developed by previous researchers. SpyCatcher could steadily bind to SpyTag by forming an isopeptide bond (2).

Usage

We aim to displaying metallothioneins MT2A and MT3 on the surface of E. coli by INPNC, which could improve the adsorption rate of heavy metal ions for the harmless treatment of deinking wastewater. However, it is tricky to verify whether a protein has been successfully displayed on the surface of bacteria. So, we introduce the Spy system. In our project, SpyCatcher is fused with INPNC and SpyTag is fused with GFP. Then, engineered bacteria which express the fused protein INPNC-his tag-SpyCatcher are treated with SpyTag-GFP. By monitoring the fluorescence intensity of bacteria, we can verify if INPNC could anchor target proteins on cell surface. Here, the basic part (BBa_K5136035) which codes the fused protein INPNC-His tag-SpyCatcher was constructed and then used for the construction of the composite part (BBa_K5136224).

Characterization

Agarose gel electrophoresis (AGE)

I0500 promoter was employed to start the expression of INPNC-his tag-spycatcher (BBa_K5136035) in E. coli BL21 (DE3). The basic part (BBa_K5136035) is a component of the composite part (BBa_K5136224). The composite part  (BBa_K5136224) constructed was introduced into the backbone plasmid (pSB1C3) through standard assembly and transformed into E. coli BL21 (DE3). The positive clones were selected, and colony PCR and gene sequencing were used to verify that the clones were correct. Target bands (2974 bp) can be observed at the position around 3000 bp. (Figure 1).

Fluorescence Intensity Determination

In order to verify the surface display effect of INPNC, plasmid pSB1C3 bearing composite part BBa_K5136224 was transformed into E. coli BL21(DE3) for subsequent verification experiments, and E. coli BL21(DE3) carrying the I0500_pSB1C3 vector was set as the control group. After induced with 0.2%(w/v) arabinose for 12 hours, the  culture solution of the experimental group(express INPNC-His tag-SpyCatcher) and the culture solution of the control group were incubated with His tag-SpyTag-GFP at 37 °C in the shaker. Cultures were taken after 12 hours, then were centrifuged to get the precipitate. The fluorescence intensity of the samples were measured. It was clearly seen from the Figure 2 that the fluorescence intensity of the experimental group was significantly higher than the fluorescence intensity of the control group. In addition, we placed the precipitation containing the control group and the experimental group under blue light. We clearly saw the green fluorescence of the experimental group excited by blue light, while the control group was contrary.(Figure 3) This fact indicated the combination between His tag-SpyTag-GFP and the INPNC-His tag-SpyCatcher displayed on the surface of E. coli BL21(DE3), demonstrating that INPNC has excellent capacity to anchor target proteins on the cell membrane.

Reference

1. M. Shimazu, A. Mulchandani, W. Chen, Cell surface display of organophosphorus hydrolase using ice nucleation protein. Biotechnology Progress 17, 76-80 (2001).
2. B. Zakeri et al., Peptide tag forming a rapid covalent bond to a protein, through engineering a bacterial adhesin. Proceedings of the National Academy of Sciences 109, E690-E697 (2012). Sequence and Features