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Updated: Jun 25, 2026
08:53
Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092
Published on: October 2, 2017
Evidence that family 35 carbohydrate binding modules display conserved specificity but divergent function
Cedric Montanier1, Alicia Lammerts van Bueren, Claire Dumon
1Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, United Kingdom.
Summary
Carbohydrate-binding modules (CBMs) in enzymes show conserved binding to uronic acids. This specificity directs plant cell wall degrading enzymes to damaged plant areas and anchors bacterial enzymes to cell walls.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Enzymes hydrolyzing complex carbohydrates are vital for life.
- Noncatalytic carbohydrate-binding modules (CBMs) target substrates for these enzymes.
- Bacterial CBMs typically correlate ligand recognition with catalytic module specificity.
Purpose of the Study:
- To investigate the structural basis and functional role of family 35 CBMs (CBM35s).
- To determine the ligand specificity of CBM35s appended to plant cell wall hydrolases and an antibacterial enzyme.
- To elucidate the role of CBM35s in enzyme targeting and bacterial cell wall attachment.
Main Methods:
- High-resolution structural studies of four distinct CBM35s.
- Analysis of CBM35s from plant cell wall hydrolases and the exo-beta-D-glucosaminidase CsxA.
- Carbohydrate-binding assays and structural comparisons.
Main Results:
- CBM35s exhibit conserved ligand-binding sites specific for glucuronic acid and/or Delta4,5-anhydrogalaturonic acid (Delta4,5-GalA).
- Delta4,5-GalA serves as a marker for pectin degradation by pectate lyases.
- CBM35s on plant hydrolases target degraded plant cell wall regions, not specific substrates.
- The CBM35 of CsxA binds uronic acids, anchoring the enzyme to the bacterial cell wall.
Conclusions:
- CBM35s direct enzymes to specific locations based on ligand presence, not just substrate identity.
- The CBM35 of CsxA employs an unusual mechanism for bacterial cell wall enzyme attachment.
- The biological role of CBM35s depends on both carbohydrate specificity and the context of target ligands.
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