Interaction of carbohydrate-binding modules with poly(ethylene terephthalate).

Area of Science:

• Biotechnology
• Polymer Science
• Biochemistry

Background:

• Poly(ethylene terephthalate) (PET) is a widely used synthetic polymer with hydrophobic properties limiting its applications.
• Biotechnological surface modification of PET can be achieved using PET hydrolyzing cutinases.
• Enzyme activity is enhanced by fusing cutinases with carbohydrate-binding modules (CBMs) to improve substrate adsorption.

Purpose of the Study:

• To identify novel CBMs with high affinity for PET.
• To characterize the molecular interactions between CBMs and PET.
• To provide insights for engineering improved PET-degrading enzymes.

Main Methods:

• Screening of eight diverse CBMs for PET binding.
• Development of a semi-quantitative method to detect CBMs on PET films.
• Molecular dynamics (MD) simulations of the CBM-PET interface.
• Experimental validation using tryptophan quenching measurements.

Main Results:

• One CBM exhibited high affinity for PET.
• MD simulations revealed an aromatic triad of tryptophan residues interacting with PET phenyl rings.
• Hydrogen bonds and the hydrophobic-to-polar contact ratio were identified as crucial for strong PET binding.
• Experimental data confirmed the interaction between CBM tryptophan residues and PET.

Conclusions:

• Novel high-affinity PET-binding CBMs were identified.
• The study elucidated the molecular basis of CBM-PET interactions, highlighting the role of aromatic residues and contact ratios.
• Findings support the engineering of enhanced PET-hydrolyzing enzymes and PET surface functionalization.