Non–Hydrolytic Disruption of Cellulose Fibres by the Binding Domain of a Bacterial Cellulase

Cellulose Binding Domains of a Phytophthora Cell Wall Protein Are Novel Pathogen-Associated Molecular Patterns

“…Characterization of several Arabidopsis cell wall mutants carrying a mutation in the cellulose synthase gene CeSA3 (i.e., cev1 and eli1 mutants) further supports the notion that the cell wall can signal stress responses in plant-pathogen interactions (Ellis and Turner, 2001;Ellis et al, 2002, Cano-Delgado et al, 2003. Thus, it is likely that the interaction of a CBD with plant cellulose microfibrils in planta results in a local nonenzymatic disruption of plant cellulose microfibrils, as has been shown for the CBDs found in cellulases and expansin (Din et al, 1991;Shpigel et al, 1998;Levy et al, 2002). Such an alteration could be sufficient to trigger defense gene expression, whereas the simultaneous interaction of the two CBDs in CBEL with microfibrils could have an additional effect on cell wall integrity and lead to necrosis.…”

Cellulose-binding domains promote hydrolysis of different sites on crystalline cellulose

“…This finding appears to contrast with previous observations indicating that CBDs by themselves might have a disrupting action on native cellulose, which must be because of different experimental conditions. Din et al (11) reported that the family II CBD of C. fimi endoglucanase CenA was able to stimulate the hydrolysis of cotton and ramie fibers when added together with the catalytic core of CenA. Pagès et al (38) observed a partial synergism on colloidal Avicel between a CBD-cohesin polypeptide (miniCipC 1 ) of C. cellulolyticum and a truncated endoglucanase (CelA 3 ), which was no longer able to associate with the CBDcohesin hybrid.…”

“…Furthermore, in some cases the binding of isolated CBDs follows a simple thermodynamic equilibrium (8) whereas in other cases it does not and appears irreversible (9,10). In contrast to family I CBDs, family II CBDs have been reported to enhance the physical disruption of cellulose fibers and to release small particles from cotton fibers (11,12). However, few studies have compared the effect of different CBDs in stimulating the activity of a given cellulase (12,13).…”

X4 Modules Represent a New Family of Carbohydrate-binding Modules That Display Novel Properties

“…CBM35, by bringing the catalytic module in the Man5C derivative CBM35-GH5 into intimate and prolonged association with DGM, increases enzyme access to the substrate leading to more efficient catalysis. The CBM does not potentiate mannanase activity in trans, indicating that the module does not mediate its affect by disrupting the interchain interactions in mannan, which is in contrast to some CBM2a proteins that enhance cellulase action by disrupting the surface of crystalline cellulose, leading to an increase in substrate access (30,31). The inability of CBM35 to improve the activity of the catalytic module of Man5C against ivory nut mannan is consistent with the observation that the CBM does not bind to the crystalline polysaccharide.…”