Part:BBa_K3771095

SoxR-PsoxS-CS-6xHis

Description

This composite part consists of the soxR gene (BBa_K3771100), promoter P_soxS (BBa_K3771048), and the cs gene (BBa_K3771012), which encodes L-cysteine sulfonic acid synthase (CS). It is used to express CS to produce taurine under oxidative stress. The soxR and the soxS gene are components of the soxRS regulon, which is important for E. coli to sense and respond to the oxidants. When SoxR protein is fully oxidized, it becomes a powerful transcription activator of the soxS promoter (P_soxS) (up to 100-fold), leading to the expression of the downstream gene^[1]. The L-cysteine sulfonic acid synthase is an enzyme that catalyzes the conversion of O-phospho-L-serine and sulfite into L-cysteine sulfonic acid (L-cysteate) and phosphate. In order to use anti-polyhistidine-tag antibodies to detect the production of CS by western blot, we add 6xHis-tag at the C-terminal of CS.

Usage and Biology

This composite part was ligated with the pSAA vector and transformed into E. coli. We conducted colony PCR to verify whether E. coli uptake the correct plasmid. The size of the PCR product was as expected. The part has been confirmed by sequencing and has no mutations.

Fig. 1. The electrophoresis result of colony PCR. M: Marker; Lane 1: pSAA-soxR-P_soxS-sfgfp (3327 bp); Lane 2, 3: pSAA-soxR-P_soxS-cs-6xHis (3876 bp).​

After the overnight incubation of E. coli with our plasmid, we diluted the bacteria culture and measured OD₆₀₀ once in a while. Until OD₆₀₀ reached 0.5, we added 0.5 mM paraquat, which served as an oxidative stress inducer, into the culture. We collected 1 ml culture each from the control group and the paraquat group at 2, 4, 6 hours after paraquat was added. Afterward, we conducted SDS-PAGE and western blot to confirm paraquat was added. Afterward, we conducted SDS-PAGE and western blot to confirm whether CS expressed successfully under the regulation of SoxR and P_soxS by oxidative stress. With the presence of SoxR, the expression level of CS in the paraquat group is high enough to be detected on SDS-PAGE (Fig. 2).

Fig. 2. The SDS-PAGE result. CS (46 kDa); –: control; PQ: 0.1 mM paraquat.

References

Pomposiello PJ, Demple B. Redox-operated genetic switches: the SoxR and OxyR transcription factors. Trends Biotechnol. 2001;19(3):109-114. doi:10.1016/s0167-7799(00)01542-0

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
  INCOMPATIBLE WITH RFC[1000]

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