Part:BBa_K2043014

GFP-FBD7

Introduction

This part corresponds to the GFP genes bound to the Fabric Binding Domain 7 (FBD7). In the context of Paris Bettencourt 2016 iGEM project, Frank&Stain, we looked for novel fabric binding domains with phage display technique in order to optimise enzymes by fusing them with different FBD.
Results from our models suggest that the addition of FBD with optimal affinity can concentrate an enzyme near the fabric surface and therefore increase stain-degrading enzymatic activity. Using the method of phage display, we isolated 40 short peptides with affinity for cotton, linen, wool, polyester or silk. Bioinformatic analysis identified sequence motifs and biophysical features associated with binding to each fabric, or nonspecific binding to several fabrics. Several peptides were selected for further analysis by quantitative ELISA. The peptides discovered were used to fuse with GFP and stain-degrading enzymes to target wine-stained fabric samples.
The peptides are identified by in vitro phage-display screening of libraries containing typically 10⁹ distinct, linear 7 amino-acid peptides against our target, in our case different fabrics- cotton, wool, silk, linen, polyester, and the library is enriched with the phages which binds to the fabric over several rounds of panning.

Table 1 Characteristics of Fabric Binding Domain. The numbers next to each fabric means the number of times the sequence was repeated in each fabric

Name	Amino Acid Sequence	Binding Affinity	Charge	Hydropathicity
FBD7	AWPYVTL	Specific to silk: Cotton(0), Linen(0), Polyester(0), Silk(1), Wool(0)	0	0.757

Testing the part

ELISA for each FBD incubated with each fabric after two rounds of washing, normalized to the level after a single round. In figure 1 we see that FBD7 binds only to Cotton and nylon with around 60% affinity


Figure 1 Fabric binding domain validation by ELISA. Control matrix repeating the procedure of panel A without phage.

After doing this assay we fuse the FBD with GFP, which is actually the part we are submitting. Then we test the fluorescence of GFP to see if the fusion itself affects the activity or the expression.

Figure 2 Bar plot showing the fluorescence of cell extracts relative to the control (No GFP expressed). Here we compare the fluorescence of different cell extract expressing Fabric Binding Domains (FBDs) with affinity for different fabrics. The part BBa_K1321357 (GFP-CBDex) was used as positive control. The blue bar correspond with the negative control (no GFP in the cell extract) whereas the green ones with those whose fluorescence was higher than the control and in red those which presented no fluorescence, maybe because lacking activity or functionality.

FBD7 didn’t pesent problems in activity as the figure 2 shows. The fluorescence of the cell extract was quiet strong even compared with the control.

Figure 3 Cell extract from E. coli expressing this part was incubated overnight in a 96 well plate with fabric placed at the bottom of the wells. Water, PBS, 5% BSA, 70% Ethanol and Catechol 30mM. The data displayed corresponds to the values after the final wash, normalised using the values from the first wash. The intensity of the colour corresponds to the GFP signal measured at that point. Excitation 475nm and emission 515nm.

According with the figure above, FBD7 presents spicificity by silk and linen when it is washed with BSA. Whereas in the ELISA analysis it doesn't show strong afinity for any fabric.

References

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]