Part:BBa_K4195100

I0500-B0034-INPNC-ttpB-his-B0015

Biology

INPNC

INPNC is a truncated form of ice nucleation protein (INP) consisting of N- and C- terminal domains (1). It is a membrane protein commonly used to displayed protein on the cell surface (2).

TTPB

TTPB is tail tubular protein B of podophage 7. It has been found that TTPB serves as ligands that recognizes the conserved Vibrio receptor Vp0980 to mediate phage adsorption. It binds with Vp0980 of Vibrio parahaemolyticus and then mediates phage adsorption and subsequent bacterial lysis(3).

Usage and design

Engineering OMVs for treating and preventing AHPND caused by the pathogen V. parahaemolyticus are a significant part of OMEGA project (Operable Magic to Efficiently Getting over AHPND). Based on the efforts of our previous projects in 2020 (AnTea-Glyphosate) and 2021 (SALVAGE), we further developed the surface display system on the OMVs released by the engineered bacteria. The usage of cargo proteins were no more limited to enzymes that are usually utilized to catalyze series bio-chemical reactions, since some receptors or ligands involved in complex protein-protein interaction (PPI) were selected as the cargo candidates. This year, we chose two classic anchor proteins, ClyA and INPNC, to construct the display cassette with various cargo proteins including rFET (receptor), rLvAPN1 (receptor), TTPB (ligand) and TTPB (ligand) (Fig. 1). On one hand, with the receptors displayed, OMVs will gain the function of neutralizing toxins secreted by V. parahaemolyticus. On the other hand, with the assistance of ligands displayed on the surface, OMVs will become a special vector to deliver antimicrobials for the specific pathogen. In summary, we have taken a step closer to the collections of extracellular functional elements (EFE), combining the OMVs, secretion systems and surface display systems which we have been dedicated to since 2020. Learn more information from our Design page.

Fig. 1 Graphic description of the expression gene circuits for display cassette designed in OMEGA project.

TTPB-his was fused to the C-terminal of INPNC to surface display for targeting V. parahaemolyticus. Arabinose-inducible system was used in the expression circuit of this part in pSB1C3 then constructed this part.We transformed the constructed plasmid into E. coli BL21(DE3) for further verification of its expression and function on the surface of E. coli and OMVs, including the interaction between TTPB and Vp0980.

Characterization

1. Identification

When constructing this circuit, colony PCR and gene sequencing were used to verify that the transformatants were correct. Target bands (4706 bp) can be observed at the position around 5000 bp (Fig. 2).

Fig. 2 DNA gel electrophoresis of the colony PCR products of BBa_K4195100_pSB1C3.

2. Characterization of displaying cargo proteins

We used BBa_I0500 promoter and RBS (BBa_B0034) to express INPNC-TTPB-his protein in E. coli BL21(DE3). The arabinose-induced overnight culture was then incubated with FITC-labeled anti-His-tag antibody in turn to verify whether the TTPB was displayed on the surface of E. coli or not.

Fig. 3 The results of immunofluorescence to characterize the function of the display system (p = 0.0277).

The ratio of fluorescence intensity (λ_Ex = 492 nm, λ_Em = 518 nm) to OD₆₀₀ of positive control (E. coli harboring BBa_K4195100) is higher than that of negative control (E. coli harboring BBa_K4195008) (Fig. 3), which indicates that our surface display system can successfully display TTPB on the surface of E. coli.

Reference

1. E. van Bloois, R. T. Winter, H. Kolmar, M. W. Fraaije, Decorating microbes: surface display of proteins on Escherichia coli. Trends. Biotechnol. 29, 79-86 (2011).

2. http://2016.igem.org/Team:TJUSLS_China.

3. M. Hu, H. Zhang, D. Gu, Y. Ma, X. Zhou, Identification of a novel bacterial receptor that binds tail tubular proteins and mediates phage infection of Vibrio parahaemolyticus. Emerg. Microbes. Infect. 9, 855-867 (2020).

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  INCOMPATIBLE WITH RFC[12]

  Illegal NheI site found at 1205
  Illegal NheI site found at 1705
  
• 21
  INCOMPATIBLE WITH RFC[21]

  Illegal BamHI site found at 1144
  Illegal BamHI site found at 3342
  
• 23
  COMPATIBLE WITH RFC[23]
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal NgoMIV site found at 1308
  Illegal NgoMIV site found at 1641
  Illegal NgoMIV site found at 2973
  Illegal AgeI site found at 979
  Illegal AgeI site found at 1728
  Illegal AgeI site found at 2059
  Illegal AgeI site found at 2329
  Illegal AgeI site found at 2884
  Illegal AgeI site found at 3298
  Illegal AgeI site found at 3742
  
• 1000
  INCOMPATIBLE WITH RFC[1000]

  Illegal SapI site found at 961
  Illegal SapI site found at 2165