Abstract
Biological degradation of Polyethylene terephthalate (PET) plastic and assimilation of the corresponding monomers ethylene glycol and terephthalate (TPA) into central metabolism offers an attractive route for bio-based molecular recycling and bioremediation applications. A key step is the cellular uptake of the non-permeable TPA into bacterial cells which has been shown to be dependent upon the presence of the key tphC gene. However, little is known from a biochemical and structural perspective about the encoded solute binding protein, TphC. Here, we report the biochemical and structural characterisation of TphC in both open and TPA-bound closed conformations. This analysis demonstrates the narrow ligand specificity of TphC towards aromatic para-substituted dicarboxylates, such as TPA and closely related analogues. Further phylogenetic and genomic context analysis of the tph genes reveals homologous operons as a genetic resource for future biotechnological and metabolic engineering efforts towards circular plastic bio-economy solutions.
Highlights
Biological degradation of Polyethylene terephthalate (PET) plastic and assimilation of the corresponding monomers ethylene glycol and terephthalate (TPA) into central metabolism offers an attractive route for bio-based molecular recycling and bioremediation applications
In order to characterise TphC, the recombinant gene, encoding the mature form, was cloned and overexpressed in Escherichia coli BL21(DE3), and the protein was purified in two consecutive chromatographic steps of metal-affinity chromatography and gel-filtration chromatography
In this study, we characterised the TphC solute-binding protein (SBP) that is a key component in the cellular uptake of TPA, the breakdown product of PET plastic[45]
Summary
Biological degradation of Polyethylene terephthalate (PET) plastic and assimilation of the corresponding monomers ethylene glycol and terephthalate (TPA) into central metabolism offers an attractive route for bio-based molecular recycling and bioremediation applications. We report the biochemical and structural characterisation of TphC in both open and TPA-bound closed conformations. This analysis demonstrates the narrow ligand specificity of TphC towards aromatic para-substituted dicarboxylates, such as TPA and closely related analogues. Recycling rate was estimated to be only ~30% in 2015 in the US, and in Europe 25% of post-consumer plastic waste still went into landfill in 2018 PET bottles were manufactured, and around 583.3 billion are forecast to be produced in 2021 The global demand for PET in 2030 is forecast to amount to 42 metric tons[10]
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