Constraction of expression plasmid in CFPS(cell-free protein synthesis)
The mutations of PETase gene had been contracted by over-lap PCR and Restriction Enzyme cutting sites(SacⅠ&EcoRⅠ) had been added to it’s ends (5’&3’) separately.
Transformation of E.coli (Trans-T1 Phage Resistant Chemically Competent Cell) with pRset_CFP-1(with AmpR) and plating on solid LB culture medium with Amp.
Cultivation the E.coli cells transformed yesterday in several 5mL liquid LB culture mediums with Amp at 37℃ for 12 hours.
Plasmid isolation of pRset_CFP-1.
Primers were designed for the target (CFP gene) within the plasmid pRset_CFP-1.
PCR with Q5-Polymerase to amplify CFP gene out of plasmid pRset_CFP-1 and add Restriction Enzyme cutting sites(XbaⅠ&SacⅠ) to it’s ends(5’&3’) separately.
Bands as expected(about 760bp) in agarose gel , gel purification of the PCR products.
XbaⅠ&SacⅠdouble restriction endonuclease digestion in CFP gene.
XbaⅠ&EcoRⅠdouble restriction endonuclease digestion in pRset_CFP-1
Bands as expected(760bp&3000bp) in agarose gel , gel purification of the digested products(3000bp).
Ligaion of digested pRset_CFP-1, digested CFP gene and digested PETase(M154L) gene in accordance with the 1:5:5 molecular ratio. The newly constructed plasmid is called pRset_CFP-1-M154L.
Transformation of E.coli (Trans-T1 Phage Resistant Chemically Competent Cell) with pRset_CFP-1-M154L(with AmpR) and plating on solid LB culture medium with Amp.
Verification : Colony PCR with fast taq Polymerase, primers: PETase-S/PETase -A, template: Colony of E.coli with plasmid pRset_CFP-1-M154L. Bands as expected(about 760bp) in agarose gel.
Cultivation the E.coli cells transformed yesterday in several 5mL liquid LB culture mediums with Amp at 37℃ for 12 hours.
Our strategy is to exchange the site-directed mutation PETase-M154L for the other 21 mutations and 1 wild type, separately.
XbaⅠ&EcoRⅠdouble restriction endonuclease digestion in pRset_CFP-1-M154L
No expected bands(3600bp&750bp) in agarose gel. We don’t find the reason why the plasmid constuced can’t be cut into the two expected bands, so we decided to change the initial strategy.
Ligaion of digested pRset_CFP-1, digested CFP gene and the rest 22 digested gene interested (including 21 PETase site-directed mutations geneand 1 wild type ) separately in accordance with the 1:5:5 molecular ratio. The newly constructed plasmid is called pRset_CFP-1-R90I (R90T, R90A, S92A, Q119A, M154A, W159H, W159M, N205L, N205V, S207T, S207A, I208V, S238F, S238V,A240P, S242I.)
We choosed 4 tubes of plasmid to express in the cell-free system firstly.
The protocol of the cell-free protein synthesis system(50 µL) we used :
MQ H2O" "7.9µL
Feeding buffer" "25µL
Mg2+ solution" "1.1µL
Gene( plasmid as template)" "1µL
Lysate" "15µL
(PS: the details of the system are not available)
Systems were expressed in 96-well plates and put the 96-well plates into the ELIASA (microplate reader) at 30℃ for 12 hours.
parallel experiments for expression in CFPS system
13 amplification at 65.0°C with 13.rev/fwd primes
PCR worked, positive control worked, no amplification of 13
The fragments of 13 were purified with PCR Purification Kit.
13 gene fragment was phosphorylated.
Show MoreInsertion of Ni promoter and ligation of 13-19-15
Ni inducible promoter was ligated into pCPC-3301 vector.
Phosphorylated 13 was ligated into pT-19-15 and transformed into E.coli via heat shock.
Single colonies were obtained by plating.
A colony PCR of Ni inducible promoter(pCPC-3301-Ni) was performed with 12 colonies.
Two of the successful ones were used to inoculate overnight cultures.
A colony PCR of pT-13-19-15 was performed with 7 colonies.
Two of the successful ones were used to inoculate overnight cultures.
Two kinds of plasmids were isolated using a miniprep kit.
Plasmids pT-13-19-15 were handed in for sequencing, which confirmed its correctness.
The sequencing results for both of them were error.
Colonies containing Ni inducible promoter were used to inoculate overnight cultures.
PCR was performed to check if the gene fragments were ligated correctly.
13_ fwd and 15_rev on pT-13-19-15
Gel electrophoresis showed that it failed.
Plasmids pCPC-3031-Ni were isolated using a miniprep kit.
Several PCRs were performed to check if the gene fragments were ligated correctly.
1.13_fwd and 13_rev on pT-13-19-15
2.19_fwd and 19_rev on pT-13-19-15
3.15_fwd and 15_rev on pT-13-19-15
4.13_fwd and 19_rev on pT-13-19-15
5.19_fwd and 15_rev on pT-13-19-15
6.13_ wd and 15_rev on pT-13-19-15 The fourth and sixth ones were not successful.
Repetition: Phosphorylated 13 was ligated into pT-19-15 and transformed into E.coli via heat shock.
Repetition: Several PCRs were performed to check if the gene fragments were ligated correctly.
1.13_fwd and 13_rev on pT-13-19-15
2.13_fwd and 19_rev on pT-13-19-15 The second one was failed.
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