Difference between revisions of "Part:BBa K2201207"

Revision as of 09:28, 25 October 2017

Expression plasmid of an aminoacyl-tRNA synthetase for AzoPhe

Aminoacyl-tRNA synthetase for incorporating phenylalanine-4‘-azobenzene (AzoF) at the amber codon.

Figure 1 shows the CDS of the AzoF-RS in a matching expression cassette based on the ONBY-part ([K1416000]) in pSB1C3.

Figure 1: Plasmid map of the BioBrick K2201207 coding for a AzoF-tRNA-synthetase system based on the ONBY-Part (K1416000). The ONBY-RS was removed by PCR and then a gene containing the AzoF-RS and matching overlaps sides was integrated through Gibson assembly.

It can be obtained by cloning the CDS in the linearized ONBY-part as shown in Figure 2.

Figure 2: History of the plasmid construction of K2201207.

This part is based on a selection experiment on the M. jannaschii TyrRS to evolve a new aaRS capable of incorporating the photoisomerizable phenylalanine-4‘-azobenzene (AzoF) by the Schultz lab. Figure 3 shows a sequence alignment of the protein sequences of the native M. jannaschii TyrRS and the AzoF-RS after the selection process.

Figure 3: Alignment of the protein sequence of the AzoF-RS and the M. jannaschii TyrRS.

Phenylalanine-4’-azobenzene is an amino acid-derivate with a photoisomerizable azobenzene moiety. Upon irradiation with a wavelength between 320 – 340 nm it switches from its more stable trans into its cis isomer due to the rotation around the N-N bond (Figure 4). The cis to trans isomerization can be thermally induced or occurs after irradiation with a wavelength > 420 nm (Figure 4) (Zimmerman et al., 1958; Bose et al., 2006; Brieke et al., 2012).

Figure 4: Structure of AzoF in cis- and trans-conformation. Switching is possible via irradiation.

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Figure 5: Absorption spectrum of AzoF in LB media after irradiation with light of 367 nm and 465 nm wavelength. The black line shows the typical absorption of AzoF in a mixed state, the trans-conformation is blue and green and the other lines show the absorption spectrum in the cis-conformation.

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Figure 6: Absorption at 476 nm (indicator for lycopene) normalized to the OD600 (indication for the cell density) to calculate the relative lycopene production of each crtI variant cultivated with AzoF in cis- and trans-conformation.

The pEVOLpAzF is available at request at CU Boulder, Bielefeld CeBiTec or addgene. For further use we recommend to clone the CDS of the AzoF-RS into a low copy plasmid like pSB3T5 or in a high copy plasmid like pSB1C3 as shown in Figure 2. The characterization was done in p15A.

Sequence and Features