O-glycosylation effects on family 1 carbohydrate-binding module solution structures

Area of Science:

• Biochemistry
• Structural Biology
• Mycology

Background:

• Family 1 carbohydrate-binding modules (CBMs) are crucial for fungal enzymes that break down plant cell walls.
• Glycosylation, the attachment of sugar molecules, significantly alters CBM properties like stability and cellulose binding.
• Understanding glycosylation's structural impact is key to optimizing these enzymes for biotechnological applications.

Purpose of the Study:

• To elucidate the molecular mechanisms by which glycosylation affects the structure and function of Family 1 CBMs.
• To investigate the role of specific mannose attachments on the cellulose-binding capabilities of Trichoderma reesei Family 1 CBM.

Main Methods:

• Solution structures of two glycoforms of a Trichoderma reesei Family 1 CBM were determined using Nuclear Magnetic Resonance (NMR) spectroscopy.
• Molecular simulations were employed to analyze the protein backbone and mannose flexibility.
• Structural data were deposited in the Protein Data Bank (PDB) and BioMagRes Bank (BMRB).

Main Results:

• Monosaccharide attachments at Ser3 and Ser14 create additional cellulose-binding platforms, aligning with the cellulose surface.
• These glycan additions significantly enhance cellulose binding affinity, consistent with previous experimental findings.
• The protein backbone structure of the CBM is largely unaffected by mannose attachment, though the mannose at Ser14 exhibits greater flexibility than at Ser3.

Conclusions:

• Covalent attachment of monosaccharides, particularly mannose at Ser3 and Ser14, acts as a key post-translational modification.
• Glycosylation provides novel binding sites and enhances the efficiency of fungal plant cell wall degrading enzymes.
• The structural insights gained can inform the design of improved enzymes for biomass degradation.