Difference between revisions of "Part:BBa K3039013"

Revision as of 20:04, 21 October 2019

SP_malE-MHETase S416A_F424N

Usage and Biology

The enzymes PETase and MHETase were first discovered in Ideonella sakaiensis in 2016 by a group of researchers in Japan. These enzymes were found to degrade polyethylene terephthalate (PET) into its monomers, terephthalic acid (TPA) and ethylene glycol (EG). PETase degrades PET into Mono-(2-hydroxyethyl)terephthalic acid (MHET), Bis(2-Hydroxyethyl) terephthalate (BHET) and TPA, the main product being MHET. MHET is further degraded by MHETase into TPA and EG. We are aiming to use mutants of these enzymes to degrade the microfibres that are coming off clothing during washing cycles. The enzymes would be secreted into a filter that captures the microfibres. This sequence is the Escherichia coli K12 (E. coli K12) codon optimized DNA of the S416A_F424N mutant MHETase with the malE signal peptide and a His tag attached. The malE signal peptide has been used in order to secrete the enzyme outside E.coli and the His tag was attached in order to more easily identify the enzymes. The wild type MHETase doesn’t show BHET degrading activity. These mutation has been reported in past papers to give MHETase the ability to degrade BHET.

The native predicted signal peptide (Met1-Ala19) was removed from the WT MHETase sequence (Palm et al 2019) and replaced with a start codon (Met), however all mutations are numbered according to the full-length WT sequence. The 27 AA malE signal peptide, which allows for excretion of the enzyme via the Sec-dependent translocation pathway (Seo et al 2019) was added to the N-terminal followed by a 13 AA His-tag. The entire amino acid sequence was codon optimised for E. coli by IDT’s on-line Codon Optimisation tool ensuring that there were no forbidden restriction sites, BsaI or SapI, to allow for TypeIIS assembly. The iGEM TypeIIS prefix and suffix were added and DNA was synthesised by IDT as a double stranded g-block. TypeIIS assembly was used to clone the resulting CDS with the T7-promoter and B0015 terminator into a high-copy number, ampicillin vector, pX1900 (University of Exeter).

Characterisation

In order to characterise our part and determine the rate of its activity and prove its functionality we have run a series of experiments. After transforming the Arctic Express, Rosetta Gami and BL21 DE3 strains of E. coli with our plasmid we induced the expression of the enzymes using IPTG. In order to confirm that the enzyme expression has been successful we ran a western blot which showed the presence of the enzyme in the soluble fractions of the sonicated cells. Afterwards the enzyme was purified and used in assays to show its functionality and determine the rate of its activity.

References

[1] Hogyun Seo, Seongmin Kim, Hyeoncheol Francis Son, Hye-Young Sagong, Seongjoon Joo, Kyung-Jin Kim; Production of extracellular PETase from Ideonella sakaiensis using sec-dependent signal peptides in E. coli (2019) Biochem. Biophys. Res. Commun. 508(1), 250-255

[2] Gottfried J. Palm, Lukas Reisky, Dominique Böttcher, Henrik Müller, Emil A. P. Michels, Miriam C. Walczak, Leona Berndt, Manfred S. Weiss, Uwe T. Bornscheuer & Gert Weber; Structure of the plastic-degrading Ideonella sakaiensis MHETase bound to a substrate (2019) Nat. Commun. 10(1717) 4

Sequences and Features