Difference between revisions of "Part:BBa K3924058"

Latest revision as of 20:56, 21 October 2021

PelB-GFP

Sequence and Features

Usage and Biology

In order to heal the intestinal tract damage, one of notable symptoms of IBD, we adopted a special therapy expressing the therapeutic proteins controllably by E.coli Nissle 1917 (EcN) in situ. The design is based on a ternary system: sensor - secretion peptide - therapeutic proteins.

Figure 1: General design of the treatment ternary system

PelB is one of candidate secretion peptides we screened out, which is a most essential element that help our therapeutic protein secrete outside the engineered bacteria and diffuse inside the patient's intestinal tract. It is a leader sequence of Erwinia carotovora endo-pectin lyase PelB^[1]. The sequence is mainly based on literature we had reviewed and modified by our condon preference system.

Functional Verification

For all candidate secretion peptides, we did codon analysis with our own software tool.(Figure 2)

Figure 2.Codon preference confidence analysis for secretion peptide, in theroy, the total GC% of EcN is 49.13%, 1st letter GC% is 55.38%, 2nd letter GC% is 42.34%, and 3rd letter GC% is 50.58%. We compare P2N and GenScript® online codon preference tool (GenSmart) analysis results for the bias from theoretical values. The lighter the squares are, the better for the codon optimization. (DNA sequence of each protein is detailed in the part page)

As for pelB, the result of codon preference is shown in Figure 3.

Figure 3.Codon preference confident analysis of pelB

The workflow of the verification of the secretion peptides' function is shown in Figure 4

Figure 4: Secretion peptide flowchart

The functional verification of secretion peptides was conducted by checking the fluorescence of the bacteria supernatant after centrifuging at 8000 rpm for 1 minute. The fluorescence is measured by microplate reader. The results are shown in Figure 5.

Figure 5: Fluorescence intensity

With RGP-GFP group (RGP is the plasmid backbone in our design) as a negative control, which doesn’t have any secretion peptide to diffuse GFP out of the protein, RGP-DsbA-GFP, however, does not show a significant difference. The fluorescence is slightly higher, but maybe due to the volatile lab environment, the significance cannot be shown. Nevertheless, we evaluate this part as a success.
With RGP-GFP group (RGP is the plasmid backbone in our design) as a negative control, which doesn’t have any secretion peptide to diffuse GFP out of the protein, RGP-PelB-GFP shows a significant difference with P=0.09. Therefore, we evaluate this part as a success.

Reference

[1] Sriwidodo S, Subroto T, Maksum I, et al.Optimization of secreted recombinant human epidermal growth factor production using pectate lyase B from Escherichia coli BL21(DE3) by central composite design and its production in high cell density culture