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| − | P<sub>C</sub> is a constitutive promoter that expresses the downstream <i>araC</i> gene. P<sub>BAD</sub> promoter is an inducible promoter, P<sub>BAD</sub> contains sequences of P<sub>C</sub>. It was verified by iGEM 2017 Amazonas_Brazil team that the induction effect of arabinose could be realized by using only <i>araC</i> and P<sub>BAD</sub>.<br><br>
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| − | ===Usage and Biology===
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| − | Arabinose operon is composed of AraC protein, P<sub>BAD</sub> and P<sub>C</sub>. The <i>araC</i> gene translates from the P<sub>C</sub> to the left.<br>
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| − | We used the P<sub>C</sub> promoter to express AraC constitutively, and constituted the sensing part of the arabinose sensing system.<br><br>
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| − | AraC gene expression product belongs to araC protein family, which is a type of two monomers with dimer structure, and each monomer with DNA binding sites of the spiral screw - corner - functional areas. It’s amino terminal determines the inducibility and it’s carboxyl terminal determines the DNA binding ability. Through this helix-rotation-helix structure, araC contacts and binds to four large sulcus regions adjacent to the DNA. <br>
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| − | [[Image: Diagram of araC binding with α-L-Arabinose.jpg|center|frame|100px|<b>Figure 1. Diagram of araC binding with α-L-Arabinose. </b> (a)α-L-arabinose, α-D-arabinose and β-D-arabinose structures. (b) A wild-type AraC combined with L-Arabinose (LA) binds to the crystalline structure of the pocket. The amino acids identified here are residues that play an important role in ligand binding.]]<br><br>
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| − | The dimerization domain is formed by folding into a pocket, combining arabinose, and dimerized by an antiparallel coiled coil. AraC stimulates RNA polymerase binding to DNA and the rate of formation of open complexes. The presence or absence of arabinose may alter the DNA contact of the upstream subunit of homodimer AraC, thereby affecting the binding of RNA polymerase. In the absence of L-arabinose, the DNA-binding domain (DBD) of the AraC dimer binds the I<sub>1</sub> and O<sub>2</sub> halves (separated by 210 bases) and inhibits transcription by forming a DNA ring upstream of the dimer. After P<sub>BAD</sub> binds to L-arabinose, the dimer changes the conformation, making DBD bind to the adjacent I<sub>1</sub> and I<sub>2</sub> halves, thus leading to transcriptional activation through interaction with RNA polymerase in P<sub>BAD</sub>. The regulatory characteristics of AraC are due to the sensitive conversion between the two conformation Pr and Pi, and the specific interaction with the inducer.<br>
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| − | [[Image: Schematic diagram of araBAD gene induced expression mechanism.jpg|center|frame|100px|<b>Figure 2. Schematic diagram of araBAD gene induced expression mechanism</b> ]]<br><br>
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| − | [[Image: AraC action mechanism diagram.jpg|center|frame|100px|<b>Figure 3. AraC action mechanism diagram</b> ]]<br><br>
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| − | In our project, we used this part together with P<sub>C</sub> and P<sub>BAD</sub> to form the arabinose sensing system, and achieved different functions by linking different target genes downstream of P<sub>BAD</sub>.<br>
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| − | Arabinose induces endotoxin expression: (链接a01+c07)<br>
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| − | Arabinose induces green fluorescent protein expression: (链接a01+c09)<br><br>
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| − | ==<b>Design</b>==
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| − | ===Design Notes===
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| − | We added some synonymous mutations to avoid part rules.<br>
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| − | ===Source===
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| − | We found this sequence data in the previous iGEM teams (Glasgow 2017) and in GenBank.<br><br>
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| − | ===References===
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