Part:BBa_K2114017

aGFPnano_HA_aHelix_cgeA

N-terminal fusion of anti-GFP nanobody to spore crust gene cgeA by an alpha helical linker.

Usage and Biology

Figure 1: Schematic representation of the fusion protein.

This part includes the anti-GFP nanobody [1] fused by an alpha helical linker [2] to the B. subtilis spore crust gene cgeA in order to be displayed on the spore surface. The hemagglutinin epitope tag was included in the fusion construct for convenient detection by specific anti-HA antibodies. The cotG gene was amplified from the genome of B. subtilis and the anti-GFP nanobody was amplified from an expression plasmid. The HA tag and the alpha helical linker were introduced by primer extensions. Both PCR fragments were assembled by Gibson cloning into pSB1C3. The fusion construct can released by XbaI and PstI and cloned alongside with an appropriate promoter into an integration vector for B. subtilis by 3A assembly [3].

Characterization

I) Surface Localization

Figure 2: Flow cytometry analysis of the surface-displayed fusion construct. Staining of wild type (not transformed) and engineered (transformed with BBa_K2114017) spores with anti-HA antibodies conjugated to Alexa Fluor 647.

The spores of B. subtilis expressing the part BBa_K2114017 were purified by lysozyme treatment to lyse remaining vegetative cells and stained with anti-HA antibodies conjugated to Alexa Fluor® 647 (Cell Signaling Technology®). The antibody could only access surface-localized HA epitopes of the expressed fusion genes and could confirm the successful display of the heterologous protein on the surface of the modified spores resulting in a slight increase of the fluorescence compared to the stained wild type spores. The low amount of fluorescent spores might be attributible to a low display efficiency using the CgeA protein as an anchor.