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.)
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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