Understanding the biological rationale for the diversity of cellulose-directed carbohydrate-binding modules in prokaryotic enzymes

Blake, Anthony W. and McCartney, Lesley and Flint, James E. and Bolam, David N. and Boraston, Alisdair B. and Gilbert, Harry J. and Knox, J. Paul (2006) Understanding the biological rationale for the diversity of cellulose-directed carbohydrate-binding modules in prokaryotic enzymes. Journal of Biological Chemistry, 281 (39). pp. 29321-29329. ISSN 0021-9258

Full content URL: http://dx.doi.org/10.1074/jbc.M605903200

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Item Type:Article
Item Status:Live Archive

Abstract

Plant cell walls are degraded by glycoside hydrolases that often contain noncatalytic carbohydrate-binding modules (CBMs), which potentiate degradation. There are currently 11 sequence-based cellulose-directed CBM families; however, the biological significance of the structural diversity displayed by these protein modules is uncertain. Here we interrogate the capacity of eight cellulose-binding CBMs to bind to cell walls. These modules target crystalline cellulose (type A) and are located in families 1, 2a, 3a, and 10 (CBM1, CBM2a, CBM3a, and CBM10, respectively); internal regions of amorphous cellulose (type B; CBM4-1, CBM17, CBM28); and the ends of cellulose chains (type C; CBM9-2). Type A CBMs bound particularly effectively to secondary cell walls, although they also recognized primary cell walls. Type A CBM2a and CBM10, derived from the same enzyme, displayed differential binding to cell walls depending upon cell type, tissue, and taxon of origin. Type B CBMs and the type C CBM displayed much weaker binding to cell walls than type A CBMs. CBM17 bound more extensively to cell walls than CBM4-1, even though these type B modules display similar binding to amorphous cellulose in vitro. The thickened primary cell walls of celery collenchyma showed significant binding by some type B modules, indicating that in these walls the cellulose chains do not form highly ordered crystalline structures. Pectate lyase treatment of sections resulted in an increased binding of cellulose-directed CBMs, demonstrating that decloaking cellulose microfibrils of pectic polymers can increase CBM access. The differential recognition of cell walls of diverse origin provides a biological rationale for the diversity of cellulose-directed CBMs that occur in cell wall hydrolases and conversely reveals the variety of cellulose microstructures in primary and secondary cell walls. © 2006 by The American Society for Biochemistry and Molecular Biology, Inc.

Additional Information:First Published [online] on July 14, 2006
Keywords:Primary cell walls, Secondary cell walls, Taxon, Cell membranes, Cellulose, Enzyme kinetics, Plant cell culture, Enzymes, carbohydrate binding protein, hydrolase, pectate lyase, polymer, Arabidopsis, article, celery, cell type, cell wall, chemical structure, controlled study, fiber, immunofluorescence, in vitro study, mucilage, nonhuman, plant seed, plant stem, priority journal, prokaryote, protein binding, taxon, tobacco, Arabidopsis, Carbohydrate Metabolism, Carbohydrates, Fluorescent Antibody Technique, Indirect, Models, Biological, Models, Molecular, Plant Proteins, Polysaccharide-Lyases, Protein Conformation, Protein Folding, Cell Walls, Enzymes, Fibrils, Apium graveolens var. dulce, Prokaryota
Subjects:C Biological Sciences > C720 Biological Chemistry
C Biological Sciences > C910 Applied Biological Sciences
Divisions:College of Science > School of Computer Science
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ID Code:12468
Deposited On:16 Dec 2013 10:47

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