Difference between revisions of "Part:BBa K185000"

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We characterize relE (BBa_K185000) by an antitoxin-toxin system, in which the downstream relE gene encoding for a stable toxin is constantly expressed, and the upstream relB (BBa_K185048) gene encodes for a labile antitoxin under the control of a temperature-sensitive RNA thermometer (BBa_K115002). Without counteracted by antitoxin RelB, RelE shuts down protein synthesis and causes the death of microbe by cleaving mRNA within the ribosomal A site [1]. In addition, the RNA thermometer allows expression of RelB at 37℃, but inhibits expression at 27℃, which leads to excess expression of RelE. As a result, we can characterize relE in a cell density-dependent manner in Escherichia coli K-12.
 
We characterize relE (BBa_K185000) by an antitoxin-toxin system, in which the downstream relE gene encoding for a stable toxin is constantly expressed, and the upstream relB (BBa_K185048) gene encodes for a labile antitoxin under the control of a temperature-sensitive RNA thermometer (BBa_K115002). Without counteracted by antitoxin RelB, RelE shuts down protein synthesis and causes the death of microbe by cleaving mRNA within the ribosomal A site [1]. In addition, the RNA thermometer allows expression of RelB at 37℃, but inhibits expression at 27℃, which leads to excess expression of RelE. As a result, we can characterize relE in a cell density-dependent manner in Escherichia coli K-12.
  
[[Image: 2019_BNU-China_BBa_K185048_pic1.png | border | center | 300px]]<br>
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[[Image: 2019_BNU-China_BBa_K185048_pic1.png | border | center | 400px]]<br>
  
 
In order to characterize the toxicity of protein encoded by relE and whether it can be inhibited by antitoxin RelB, we take E. coli introduced with a vector with the same backbone as control group.  
 
In order to characterize the toxicity of protein encoded by relE and whether it can be inhibited by antitoxin RelB, we take E. coli introduced with a vector with the same backbone as control group.  

Revision as of 10:17, 9 October 2019

RelE toxin+Rbs30

RelE is a toxin protein. And this part is composed with rbs BBa_B0030.

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]


Characterized by BNU-China 2019

We characterize relE (BBa_K185000) by an antitoxin-toxin system, in which the downstream relE gene encoding for a stable toxin is constantly expressed, and the upstream relB (BBa_K185048) gene encodes for a labile antitoxin under the control of a temperature-sensitive RNA thermometer (BBa_K115002). Without counteracted by antitoxin RelB, RelE shuts down protein synthesis and causes the death of microbe by cleaving mRNA within the ribosomal A site [1]. In addition, the RNA thermometer allows expression of RelB at 37℃, but inhibits expression at 27℃, which leads to excess expression of RelE. As a result, we can characterize relE in a cell density-dependent manner in Escherichia coli K-12.

2019 BNU-China BBa K185048 pic1.png

In order to characterize the toxicity of protein encoded by relE and whether it can be inhibited by antitoxin RelB, we take E. coli introduced with a vector with the same backbone as control group.

As is shown in Fig.1, there is nearly no difference of the relative population density between control and experimental groups at 37℃, which indicates RelE interacts with RelB and thereby the cleavage of mRNA by RelE is inhibited. However, the population density of experimental group shows a significant decrease compared to control group at 27℃, which indicates the protein encoded by relE is lethal to E. coli.

2019 BNU-China BBa K185048 pic2.png

Figure 1 Relative population density at different temperatures

With properties of relE, we can construct a kill switch in engineered microbe to ensure lab safety.

Experimental approach

1. Transform the plasmids into E. coli DH5α competent cells. 2. A strain containing a vector with same backbone is used as control. Experimental groups and control groups are both cultured in 60mL LB-ampicillin (50 ng/µl) medium overnight at 37℃, 200rpm; 3. Equally divide each group into two flasks, which is 30mL respectively. One of each group is cultured at 27℃, 200rpm and the other at 37℃, 200rpm; 4. Extract 5μl samples of each culture system every 6 hours. Diluted all of the samples to 107 times and then spread them on solid LB-ampicillin (50 ng/µl) medium separately; 5. Count the number of colonies in 5 cm2 per plate after cultured for 24 hours at 37℃ 6. Three repicas are tested in each group.

Reference

[1] Overgaard M , Borch J , Gerdes K . RelB and RelE of Escherichia coli Form a Tight Complex That Represses Transcription via the Ribbon–Helix–Helix Motif in RelB[J]. Journal of Molecular Biology, 2009, 394(2):0-196.

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]