Team:Shiyan SY China/Design
You have to believe in yourself. That’s the secret of success.
—— Charles Chaplin
Note: F1:EcoRI-Constitutive promoter-RNA thermometer-rbs-ompA-Hind III,F2:HindIII-opdA-DNA spacer-Spe, F3:Xbal-RecA(SOS)-rbs-Hind III, F4: Hind III-ccdB-Pstl.
Faced with the stress of human pollution such as pesticides, nature itself has evolved many methods to deal with these problems. For example, many natural micro-organisms contain enzymes to degrade organophosphorus pesticides. Currently the micro-organisms which are capable to degrade organophosphorus pesticides include bacteria, fungus, actinomycete and alga. As the research goes further, people find that these degrading effects come from secreting an enzyme, which can hydrolyze phosphoester bonds, organophosphorus degradation enzyme. Because each organophosphorus pesticide has similar structure and protein sequence, one kind of organophosphorus degradation enzyme is capable todegrade multiple kinds of organophosphorus pesticides. Organophosphorus-degradation enzyme has been mostly recognized as the best method to eliminate pesticide residues currently. At present, many enzymes have been identified to be used to degrade organophosphate pesticides. Among these enzymes, the organophosphorus-degradation enzyme (opdA) which comes from Agrobacterium radiobacter P230 has wider targets and higher enzyme-catalyst efficiency. In recent years, the research on the structure and function of organophosphorus-degradation enzyme has gained promising progress,. Thus, it is possible to improve the properties of organophosphorus-degradation enzyme through genetic engineering and protein engineering method, which meet requirements of different applications.
The organophosphorus-degradation enzyme (opdA) gene opdA （NCBI genbank：Accession: AY043245.2） programmed by Agrobacterium radiobacter contains 1,155 nucleic acids, programming 384 amino acid residues. The N-terminal of protein sequence is the signal peptide while the C-terminal is the degradation-enzyme sequence. The nucleic acid sequence and amino acid sequence are as follows:
at gcaaacgaga agagatgcac ttaagtctgc ggccgcaata actctgctcg gcggcttggc tgggtgtgca agcatggccc gaccaatcgg tacaggcgat ctgattaata ctgttcgcgg ccccattcca gtttcggaag cgggcttcac actgacccat gagcatatct gcggcagttc ggcgggattc ctacgtgcgt ggccggagtt tttcggtagc cgcaaagctc tagcggaaaa ggctgtgaga ggattacgcc atgccagatc ggctggcgtg caaaccatcg tcgatgtgtc gactttcgat atcggtcgtg acgtccgttt attggccgaa gtttcgcggg ccgccgacgt gcatatcgtg gcggcgactg gcttatggtt cgacccgcca ctttcaatgc gaatgcgcag cgtcgaagaa ctgacccagt tcttcctgcg tgaaatccaa catggcatcg aagacaccgg tattagggcg ggcattatca aggtcgcgac cacagggaag gcgaccccct ttcaagagtt ggtgttaaag gcagccgcgc gggccagctt ggccaccggt gttccggtaa ccactcacac gtcagcaagt cagcgcgatg gcgagcagca ggcagccata tttgaatccg aaggtttgag cccctcacgg gtttgtatcg gtcacagcga tgatactgac gatttgagct acctaaccgg cctcgctgcg cgcggatacc tcgtcggttt agatcgcatg ccgtacagtg cgattggtct agaaggcaat gcgagtgcat tagcgctctt tggtactcgg tcgtggcaaa caagggctct cttgatcaag gcgctcatcg accgaggcta caaggatcga atcctcgtct cccatgactg gctgttcggg ttttcgagct atgtcacgaa catcatggac gtaatggatc gcataaaccc agatggaatg gccttcgtcc ctctgagagt gatcccattc ctacgagaga agggcgtccc gccggaaacg ctagcaggcg taaccgtggc caatcccgcg cggttcttgt caccgaccgt gcgggccgtc gtgacacgat ctgaaacttc ccgccctgcc gcgcctattc cccgtcaaga taccgaacga tga
MQTRRDALKSAAAITLLGGLAGCASMARPIGTGDLINTVRGPIPVSEAGFTLTHEHICGSSAGFLRAWPEFFGSRKALAEKAVRGLRHARSAGVQTIVDVSTFDIGRDVRLLAEVSRAADVHIVAATGLWFDPPLSMRMRSVEELTQFFLREIQHGIEDTGIRAGIIKVATTGKATPFQELVLKAAARASLATGVPVTTHTSASQRDGEQQAAIFESEGLSPSRVCIGHSDDTDDLSYLTGLAARGYLVGLDRMPYSAIGLEGNASALALFGTRSWQTRALLIKALIDRGYKDRILVSHDWLFGFSSYVTNIMDVMDRINPDGMAFVPLRVIPFLREKGVPPETLAGVTVANPARFLSPTVRAVVTRSETSRPAAPIPRQDTER
at gcaaacgaga agagatgcac ttaagtctgc ggccgcaata actctgctcg gcggcttggc tgggtgtgca agcatggccc gaccaatcgg tacaggcgat ctgattaata ctgttcgcgg ccccattcca gtttcggaag cgggcttcac actgacccat gagcatatct gcggcagttc ggcgggattc ctacgtgcgt ggccggagtt tttcggtagc cgcaaagctc tagcggaaaa ggctgtgaga ggattacgcc atgccagatc ggctggcgtg caaaccatcg tcgatgtgtc gactttcgat atcggtcgtg acgtccgttt attggccgaa gtttcgcggg ccgccgacgt gcatatcgtg gcggcgactg gcttatggtt cgacccgcca ctttcaatgc gaatgcgcag cgtcgaagaa ctgacccagt tcttcctgcg tgaaatccaa catggcatcg aagacaccgg tattagggcg ggcattatca aggtcgcgac cacagggaag gcgaccccct ttcaagagtt ggtgttaaag gcagccgcgc gggccagctt ggccaccggt gttccggtaa ccactcacac gtcagcaagt cagcgcgatg gcgagcagca ggcagccata tttgaatccg aaggtttgag cccctcacgg gtttgtatcg gtcacagcga tgatactgac gatttgagct acctaaccgg cctcgctgcg cgcggatacc tcgtcggttt agatcgcatg ccgtacagtg cgattggtct agaaggcaat gcgagtgcat tagcgctctt tggtactcgg tcgtggcaaa caagggctct cttgatcaag hgcgctcatcg accgaggcta caaggatcga atcctcgtct cccatgactg gctgttcggg ttttcgagct atgtcacgaa catcatggac gtaatggatc gcataaaccc agatggaatg gccttcgtcc ctctgagagt gatcccattc ctacgagaga agggcgtccc gccggaaacg ctagcaggcg taaccgtggc caatcccgcg cggttcttgt caccgaccgt gcgggccgtc gtgacacgat ctgaaacttc ccgccctgcc gcgcctattc cccgtcaaga taccgaacga tga
MQTRRDALKSAAAITLLGGLAGCASMARPIGTGDLINTVRGPIPVSEAGFTLTHEHICGSSAGFLRAWPEFFGSRKALAEKAVRGLRHARSAGVQTIVDVSTFDIGRDVRLLAEVSRAADVHIVAATGLWFDPPLSMRMRSVEELTQFFLREIQHGIEDTGIRAGIIKVATTGKATPFQELVLKAAARASLATGVPVTTHTSASQRDGEQQAAIFESEGLSPSRVCIGHSDDTDDLSYLTGLAARGYLVGLDRMPYSAIGLEGNASALALFGTRSWQTRALLIKALIDRGYKDRILVSHDWLFGFSSYVTNIMDVMDRINPDGMAFVPLRVIPFLREKGVPPETLAGVTVANPARFLSPTVRAVVTRSETSRPAAPIPRQDTER
In this project, we will use E. Coli to construct genetically engineered bacteria which can secrete organophosphorus-degradation enzyme opdA protein, to eliminate the pesticides.
Genetically engineered bacteria are bacteria which can channel target gene into bacteria to express the genes and produce required protein.
Currently, the mostly used genetically engineered bacteria all over the world are still E. Coli. E. Coli have explicit genetic background, fast growth rate, limited antibiotics resistance, Thus, E. Coli, are easy to be used in any production magnitude from laboratory to industry production. (For example: scientists introduced human insulin gene into E. Coli genome. E. Coli can express functional human insulin protein, which is used as a medicine for diabetes treatment. Human insulin production from E. coli has been applied to industry and this method is also widely used in biotech industry for other drug purposes In 1981, human insulin gene products were put into market and solved the problem of lack of insulin sources).
An RNA thermometer (or RNA thermosensor) is a temperature-sensitive non-coding RNA molecule which regulates gene expression. RNA thermometers often regulate genes required during either a heat shock or cold shock response. In general, RNA thermometers operate by changing their secondary structure in response to temperature fluctuations. This structural transition can then expose or occlude important regions of RNA such as a ribosome binding site, which then affects the translation rate of a nearby protein-coding gene.
Below is a schematic diagram of Thermometer RNA:
In this project, the Thermometer RNA we use has a sensitive temperature of 32℃, which means in environment above 32C, RNA translation process can be started. Its DNA sequence is as follows:
Ccgggcgcccttcgggggcccggcggagacgggcgccggaggtgtccgacgcctgctcgtccagtctttgctcagtggaggattactag
In this project, to secrete the opdA enzyme from inside the bacteria to outside, an ompA signal peptide is introduced into the construction. By adding this secreting peptide, OpdA is secreted outside the E. Coli, without its accumulating inside.
Signal peptide often refers to a N-terminal amino acid sequence which is used to direct the trans-membrane process in newly synthesized proteins. There is a segment of RNA area programming hydrophobic amino acid sequence which is generally behind the start codon. This amino acid sequence is called signal peptide sequence, which introduces protein into sub-cellular organelles which contain different membrane structures. If the function of this signal peptide is to secrete protein outside the cell walls, this signal peptide is called secretion signal peptide.
As we know, on natural conditions, ompA which exists inside Agrobacterium radiobacter bacteria has its own signal peptide. However, this original signal peptide is only used by Agrobacterium radiobacter and is not necessarily functional inE. Coli. Therefore, we need to select an E. colisignal peptides to achieve our plan.
The ompA signal peptide used in this project is one of the E. coli secreting signal peptides and can lead secretion of its downstream protein outside of its host E. coli. The DNA sequence of this signal peptide is as follows:
Atgaaaaaaaccgctatcgcgatcgcagttgcactggctggtttcgctaccgttgcgcaggcc
In this project, we consider not only how to use genetically engineered bacteria to eliminate organophosphorus, but also after organophosphorus is eliminated, how we should deal with the rest genetically engineered bacteria. Genetically engineered bacteria, after all, come from E. coli. We don’t want them released into environment or remaining on the surface of fruits and vegetables. Thus we must design a method to eliminate them. Consequently, we decide to design a suicide gene into our genetically engineered bacteria, which is inactivated under normal condition and only activated under special environments to eliminate the bacteria and avoid “secondary pollution”.
To achieve the above goal, we select suicide gene ccdb. ccdB is a known toxin system, which exists in pathogenic E. coli F plasmid. The ccdB gene programs a toxin protein CcdB. On conditions where there is a lack of antitoxin, CcdB poisons gyrase inside cells to interfere with the DNAsynthesis and damage host cells. The ccdb sequence we use in this project is as follows:
Atgcagtttaaggtttacacctataaaagagagagccgttatcgtctgtttgtggatgtacagagtgatattattgacacgcccgggcgacggatggtgatccccctggccagtgcacgtctgctgtcagataaagtctcccgtgaactttacccggtggtgcatatcggggatgaaagctggcgcatgatgaccaccgatatggccagtgtgccggtctccgttatcggggaagaagtggctgatctcagccaccgcgaaaatgacatcaaaaacgccattaacctgatgttctggggaatataa
In the project we chose a RecA(SOS) promoter to control to suicide gene ccdB to express. When the bacteria receive ultraviolet lights, DNA injurｙ activate the RecA repairing system. The system can activate RecA(SOS) promoter to drive the downstream ccdB suicide gene’s transcription. In this way, we can control our engineering bacteria by eliminating them with ultraviolet rays to avoid secondary pollution.
The ccdb sequence we use in this project is as follows:
Aacaatttctacaaaacacttgatactgtatgagcatacagtataattgcttcaacagaacatattgactatccggtattacccggcatgacaggagtaaaaatggctatcgacgaaaacaaacagaaagcgttggcggcagcactgggccagattgagaaacaatttggtaaaggctccatcatgtaataa
(1)The strong initiation sequence used in this project referred to BB_J23106 from igem
(2)The RNA thermometer sequence used in this project referred to BB_K115017 from igem
(3)The organophosphorus-degradation enzyme opdA gene sequence used in this project referred to BB_K21509, BB_K215091 and BB_K1010008 from igem
(4)The repair enzyme induced promoter RecA (SOS) sequence used in this project referred to BB_J22106 from igem
(5)The suicide gene ccdB sequence used in this project referred to BB_K145151 and BB_K1010007 from igem
(6)The ompA signal peptide sequence used in this project referred to sequence with the code AJ617284.1 from GenBank
© 2015 Shiyan_SY_China iGEM Team. All rights reserved.
