Structural basis of terephthalate recognition by solute binding protein TphC

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.

Structural Insights into (Tere)phthalate-Ester Hydrolysis by a Carboxylesterase and Its Role in Promoting PET Depolymerization

“…Additionally, I. sakaiensis was found to metabolize TPA and possess a specific TPA translocation system . However, the lack of a specific transporter machinery for MHET in I.…”

“…Additionally, I. sakaiensis was found to metabolize TPA and possess a specific TPA translocation system. 39 However, the lack of a specific transporter machinery for MHET in I. sakaiensis invalidates the assumption that the extracellular PETase and intracellular MHETase can work synergistically during the bacterial assimilation of PET. Similarly, TfCa and TfCut2, the artificially synergistic enzymes in PET depolymerization, are derived from the same species of T. fusca .…”

Global plastic upcycling during and after the COVID-19 pandemic: The status and perspective

“…Industry-scale biodegradation was limited by the time-consuming natural processing, and as a result, enzyme discovery, protein engineering, kinetics, and computational studies provided potential solutions [129] , [130] , [131] , [132] , [133] , [134] , [135] , [136] . However, industrial application of biodegradating plastics using biocatalysts like carboxyl ester hydrolases, including lipases, esterases, cutinases, and PETases, have not been achieved yet due to a number of reasons (e.g., instability and activity reduction in even mild conditions) [133] .…”

An Ultra-Sensitive Comamonas thiooxidans Biosensor for the Rapid Detection of Enzymatic Polyethylene Terephthalate (PET) Degradation

“…(B) Physical map of the genomic region coding for the TPA uptake and catabolic genes in C. thiooxidans S23. Uptake is presumably facilitated via the transporter subunits TpiA and TpiB together with the substrate binding protein TphC ( 26 , 43 ). OM, outer membrane; IM, inner membrane.…”