Coding
SRTF1

Part:BBa_K3889021

Designed by: Prameya Garge, Ashwin Sharma   Group: iGEM21_IISER-Tirupati_India   (2021-10-02)


Steroid Responsive Transcription Factor1 (SRTF1)

Steroid Responsive Transcription Factor (SRTF1) is a bacterial transcription factor that can respond to progesterone in a concentration-dependent manner. SRTF1 binds to its binding site (BBa_K3889030) resulting in inhibition of gene expression. Now as progesterone enters the system SRTF1 binds to progesterone leaving its binding site free for the transcription machinery to start working. This results in a progesterone inducible gene expression. [1]

T--IISER-Tirupati India--SRTF1 repression.png


Contribution: Waseda_Tokyo 2022

Waseda_Tokyo 2022 used this part in the aim for detecting progesterone in cell-free protein synthesis (CFPS) system in E.coli. We demonstrated that this part did not work in E.coli. We transformed this plasmid into E.coli BL21(DE3)Star strain, and made cell-free extracts enriched with the protein. Fig. 1 shows the result of SDS-PAGE performed with the bacterial extract. SRTF1 optimized for E.coli BBa_K4158012 is shown as a control. As shown in Fig. 1., the molecular mass of the protein optimized for Bacillus subtilis was smaller than that of SRTF1 (22kDa). Thus, we found that SRTF1 gene optimized for Bacillus subtilis was not fully translated in E.coli due to the difference in codon usage in these two organisms.


Fig. 1. The result of SDS-PAGE (SRTF1)


The nucleotide sequence of this part BBa K3889021 (B.subtilis optimized SRTF1 gene) is shown below. Bold letters represent low-usage codons in E.coli [2]

atg/tct/agt/act/gcg/gag/aga/ata/cgg/cca/gga/aga/agc/ggg/att/ctc/gct/gct/gcc/act/cgc/ctc/ttc/gcg/acg/cac/gga/gtg/tct/ggc/aca/tca/tta/caa/caa/ata/gcc/gat/gcc/act/ggt/atc/ aca/aaa/gct/gct/gta/tac/cat/cac/ttc/cct/acc/aaa/gaa/gaa/gtg/gtc/gtc/gct/gtc/ttg/gcg/cct/gcc/ctt/gag/gcc/atc/caa/ggc/atc/gtt/aga/aca/gca/ggg/gct/cac/gaa/gat/cct/cgc/gcc/ gct/acc/gag/gca/gcg/att/att/gga/ctc/gcg/gac/caa/gca/gtc/acg/cat/cgc/cag/cgc/tgg/gct/gtt/ctg/tta/caa/gat/gca/gca/gta/gaa/gaa/tac/gtc/cgt/aac/aat/cca/gac/cac/gat/gag/ttg/ ttc/act/cgt/ctg/aga/tta/ctg/ctt/act/ggc/ccc/gat/ccg/acc/cct/ggg/act/aga/ctg/caa/gtg/tcc/ctc/ttc/ttg/tct/ggt/ctt/ttg/ggg/cca/gca/caa/gat/cct/tct/tgc/gca/gat/ata/gac/gac/gat/gcg/ tta/aga/gcg/gga/atc/gta/cgt/gcg/ggc/cgt/aga/ctg/ctc/ttg/gcg/gat/gac/gac/gct/taa


Parts Improvement: Waseda_Tokyo 2022

BBa_K4158012

This part contains RBS and SRTF1-SSGSSG-TEV-His coding site. SRTF1 is a bacterial(steroid metabolizing bacterium; Pimelobacter simplex) transcription factor.

SRTF1 sequence is optimized to E. coli codon. This part is the improvement of BBa_K3889021(B. sub optimized SRTF1).

Fig. 1. progesterone detector gene circuit

Design SRTF1 amino acid sequence was cited from a previous paper[1].

We designed this part by

  • optimizing SRTF1 amino sequences to E.coli codon by using GeneArt(Thermo).
  • optimizing the 5'UTR by using RBS calculator and RNA fold.

Then, we inserted the fragment into pET26b(+) vector.

Results

In order to detect progesterone in vitro, we transformed this part into BL21(DE3)Star strain and prepared crude extracts which were pre-enriched with the transcription factor, SRTF1.

Fig. 2. Preparation of SRTF1-enriched extract

We also prepared cell-free extract enriched with the B. subtilis optimized SRTF1, using BBa_K3889021. Then, we performed SDS-PAGE to compare the expression of the protein in E. coli with both of the parts.

From Fig. 3., we could confirm that SRTF1(22kDa) codon-optimized for E.coli was successfully expressed in E. coli. On the other hand, the molecular mass of the protein optimized for Bacillus subtiliswas smaller than that of SRTF1 (22kDa). Thus, we found that SRTF1 gene optimized for Bacillus subtilis was not fully translated inE.coli due to the difference in codon usage in these two organisms.

Fig. 3. The result of SDS-PAGE (SRTF1)


We also performed cell-free protein synthesis reaction with the extracts, using BBa_K4158010 as the reporter plasmid. Fig. 4. shows the result of the experiment. We added 100uM of progesterone in the final concentration. We demonstrated that this part could detect progesterone in the cell-free protein synthesis system.

Fig. 4. comparison of result of progesterone sensing by SRTF1

We could confirm below from Fig. 4..

  • The plain(BBa_K4158012): there is a significant difference of the fluorescence between progeterone added and not added.
  • The shaded(BBa_K3889021): there isn't a significant difference of the fluorescence between progeterone added and not added..


Thus, we succeeded in engineering SRTF1-expressing plasmid which works in E.coli, as a part improvement of BBa_K3889021. BBa_K4158012 is said to be an improvement of the existing part in that it allows SRTF1 to be expressed not only in Bacillus subtilis but also in the heterologous organism E.coli.


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]


References

1. Grazon, C., Baer, R. C., Kuzmanović, U., Nguyen, T., Chen, M., Zamani, M., Chern, M., Aquino, P., Zhang, X., Lecommandoux, S., Fan, A., Cabodi, M., Klapperich, C., Grinstaff, M. W., Dennis, A. M., & Galagan, J. E. (2020). A progesterone biosensor derived from microbial screening. In Nature Communications (Vol. 11, Issue 1). Springer Science and Business Media LLC. https://doi.org/10.1038/s41467-020-14942-5

2. Don Lorimer et al. Gene Composer: Database Software for Protein Construct Design, Codon Engineering, and Gene Synthesis. BMC Biotechnology 9(1):36(2009).

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