Evidence that family 35 carbohydrate binding modules display conserved specificity but divergent function

Montanier, Cedric and Van Bueren, Alicia Lammerts and Dumon, Claire and Flint, James E. and Correia, Marcia A. and Prates, Jose A. and Firbank, Susan J. and Lewis, Richard J. and Grondin, Gilles G. and Ghinet, Mariana G. and Gloster, Tracey M. and Herve, Cecile and Knox, J. Paul and Talbot, Brian G. and Turkenburg, Johan P. and Kerovuo, Janne and Brzezinski, Ryszard and Fontes, Carlos M. G. A. and Davies, Gideon J. and Boraston, Alisdair B. and Gilbert, Harry J. (2009) Evidence that family 35 carbohydrate binding modules display conserved specificity but divergent function. Proceedings of the National Academy of Sciences, 106 (9). pp. 3065-3070. ISSN 0027-8424

Full content URL: http://dx.doi.org/10.1073/pnas.0808972106

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Abstract

Enzymes that hydrolyze complex carbohydrates play important roles in numerous biological processes that result in the maintenance of marine and terrestrial life. These enzymes often contain noncatalytic carbohydrate binding modules (CBMs) that have important substrate-targeting functions. In general, there is a tight correlation between the ligands recognized by bacterial CBMs and the substrate specificity of the appended catalytic modules. Through high-resolution structural studies, we demonstrate that the architecture of the ligand binding sites of 4 distinct family 35 CBMs (CBM35s), appended to 3 plant cell wall hydrolases and the exo-β-D-glucosaminidase CsxA, which contributes to the detoxification and metabolism of an antibacterial fungal polysaccharide, is highly conserved and imparts specificity for glucuronic acid and/or �4,5-anhydrogalaturonic acid (�4,5-GalA). �4,5-GalA is released from pectin by the action of pectate lyases and as such acts as a signature molecule for plant cell wall degradation. Thus, the CBM35s appended to the 3 plant cell wall hydrolases, rather than targeting the substrates of the cognate catalytic modules, direct their appended enzymes to regions of the plant that are being actively degraded. Significantly, the CBM35 component of CsxA anchors the enzyme to the bacterial cell wall via its capacity to bind uronic acid sugars. This latter observation reveals an unusual mechanism for bacterial cell wall enzyme attachment. This report shows that the biological role of CBM35s is not dictated solely by their carbohydrate specificities but also by the context of their target ligands. © 2009 by The National Academy of Sciences of the USA.

Keywords:carbohydrate, carbohydrate binding module, carbohydrate binding protein, carbohydrate derivative, galacturonic acid, glucosaminidase, glucuronic acid, hydrolase, unclassified drug, uronic acid, article, bacterial cell wall, bacterium adherence, carbohydrate analysis, enzyme binding, enzyme specificity, ligand binding, plant cell, priority journal, protein carbohydrate interaction, protein function, protein structure, X ray crystallography, Actinomycetales, Carbohydrate Metabolism, Carbohydrates, Cell Adhesion, Cell Wall, Galectin 3, Ligands, Models, Molecular, Molecular Structure, Mutation, Protein Binding, Substrate Specificity, Thermodynamics, Uronic Acids, Bacteria (microorganisms)
Subjects:B Subjects allied to Medicine > B100 Anatomy, Physiology and Pathology
C Biological Sciences > C100 Biology
Divisions:College of Science > School of Life Sciences
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ID Code:12462
Deposited On:29 Oct 2013 10:30

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