Part:BBa_K346096
PmerT promoter-GFP(E0840)
This part was designed to characterize PmerT. When this plasmid was transformed to the bacteria expressing its correspondent activator MerR, the strain would be induced by Hg(II) to express GFP. The relationship between GFP intensity and the Hg(II)'s concentration helped us learn the character of PmerT. The strain we used contained the J23103-merR(BBa_K346009) in backbone pSB1A2 and this part was in backbone pSB3K3.
We constructed this part to calculate the expression level of GFP under the wild type PmerT. The plot is done by using different concentration of Hg to induce the promoter and to calculate the GFP intensity. In detail, when the concentration of Hg(II) in the cytosol is different, the active form of MerR dimer will increase and the possibility that it will active PmerT promoter will increase.
Figure 1 Hg(II) induced response curve of PmerT-GFP The GFP intensity when cultured by different concentration of Hg(II). Cultures were diluted 1:100 in LB and grown to final OD600 0.6. Then different concentration of Hg(II) was added to the culture and we put the tube in the shaker for 2 hours in 30 ℃. Then we suspended the culture with 1% PBS and measure the GFP intensity using a microplate reader.
Part BBa_K34020-BBa_K34025 are 6 mutants of this part. We constructed a library of PmerT promoter with 6 mutants carefully characterized.
it could be expected that mutation at the dyad domain II would change the Ka of MerR-DNA interactions. Thus we mutated the semiconserved sites and left the conserved sites constant.
The approach is generally based upon degenerate primer PCR, with the combination of a ‘DNA shuffling’ procedure, that is performed on the target DNA sequence; the resulting library of variants is then screened for the desired feature, and selected isolates are subjected to a repeated procedure(Fig.6).
Figure.2. Library construction. We performed a degenerate primer PCR on the merTPCAD wild-type promoter region of the alterable sites. The resulting PCR fragments, each potentially contained one or more mutation sites at a restricted location.
Figure.3. Dose-response curves of mutants. Among all these candidates, mutant1, 3, 25, 44, 85, 88 (also shown in Fig 3) were selected for the final careful characterization during which a higher concentration resolution was exploited. Then the dose-response curves were fitted by Hill function.
Figure.4 Sequenc comparison of the mutants
It can be observed that mutations at the semiconserved region of PmerT promoter significantly influenced the response behavior of MerR/PmerT pair(Fig.7). It is probably because that the mutations alter the binding affinity between MerR and PmerT promoter. As a result of this, different sensitivity (higher or lower than the wild-type) PmerT promoters were gained by us.
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21COMPATIBLE WITH RFC[21]
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000INCOMPATIBLE WITH RFC[1000]Illegal BsaI.rc site found at 730
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