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

DOI: 10.1073/pnas.0808972106 DOI Help
PMID: 19218457 PMID Help

Authors: Cedric Montanier (University of Newcastle) , Alicia Lammerts Van Bueren (Department of Biochemistry and Microbiology, University of Victoria) , Claire Dumon (Newcastle University) , James E. Flint (Newcastle University) , Márcia Correia (1CIISA - Faculdade de Medicina Veterinária, Universidade Técnica de Lisboa) , Jose A. Prates (Universidade Te´ cnica de Lisboa) , Susan Firbank (Institute for Cell and Molecular Biosciences, Newcastle University) , Rick Lewis (Newcastle University) , Gilles G. Grondin (Universite´ de Sherbrooke) , Mariana G. Ghinet (Universite´ de Sherbrooke) , Tracey M. Gloster (The University of York) , Cecile Herve (University of Leeds) , J. Paul Knox (University of Leeds) , Brian G. Talbot (Universite´ de Sherbrooke) , Johan Turkenburg (University of York) , Janne Kerovuo (Verenium Corporation) , Ryszard Brzezinski (Universite´ de Sherbrooke) , Carlos M. G. A. Fontes (Universidade Tecnica de Lisboa) , Gideon J. Davies , Alisdair B. Boraston (University of Victoria) , Harry J. Gilbert (Newcastle University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 106 (9) , PAGES 3065 - 3070

State: Published (Approved)
Published: March 2009

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-?-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.

Journal Keywords: Carbohydrate; Carbohydrates; Cell;Galectin; Ligands; Models; Molecular; Mutation; Protein; Substrate; Thermodynamics; Uronic Acids

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: I03-Macromolecular Crystallography

Added On: 29/09/2011 22:15

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