Recognition of cello-oligosaccharides by a family 17 carbohydrate-binding module: an X-ray crystallographic, thermodynamic and mutagenic study.

The crystal structure of the Clostridium cellulovorans carbohydrate-binding module (CBM) belonging to family 17 has been solved to 1.7 A resolution by multiple anomalous dispersion methods. CBM17 binds to non-crystalline cellulose and soluble beta-1,4-glucans, with a minimal binding requirement of cellotriose and optimal affinity for cellohexaose. The crystal structure of CBM17 complexed with cellotetraose solved at 2.0 A resolution revealed that binding occurs in a cleft on the surface of the molecule involving two tryptophan residues and several charged amino acids. Thermodynamic binding studies and alanine scanning mutagenesis in combination with the cellotetraose complex structure allowed the mapping of the CBM17 binding cleft. In contrast to the binding groove characteristic of family 4 CBMs, family 17 CBMs appear to have a very shallow binding cleft that may be more accessible to cellulose chains in non-crystalline cellulose than the deeper binding clefts of family 4 CBMs. The structural differences in these two modules may reflect non-overlapping binding niches on cellulose surfaces.

Notenboom V ，Boraston AB ，Chiu P ，Freelove AC ，Kilburn DG ，Rose DR ... -  《JOURNAL OF MOLECULAR BIOLOGY》

Molecular determinants of ligand specificity in family 11 carbohydrate binding modules: an NMR, X-ray crystallography and computational chemistry approach.

Viegas A ，Brás NF ，Cerqueira NM ，Fernandes PA ，Prates JA ，Fontes CM ，Bruix M ，Romão MJ ，Carvalho AL ，Ramos MJ ，Macedo AL ，Cabrita EJ ... -  《FEBS Journal》

Recognition of cellooligosaccharides by a family 28 carbohydrate-binding module.

The crystal structures of a carbohydrate-binding module (CBM) family 28 domain of endoglucanase Cel5A from Clostridium josui have been determined in ligand-free and complex forms with cellobiose, cellotetraose, and cellopentaose as the first complex structures of this family. In the cleft of a beta-sandwich fold, the ligands are recognized by stacking interactions and hydrogen bonds. Conformations of the bound cellooligosaccharides are similar to those in crystals and solution but clearly different from the cellulose structure. Interestingly, the glucan chain bound on CBM28 is in the opposite direction of that bound to CBM17, although these families share significant structural similarity.

Tsukimoto K ，Takada R ，Araki Y ，Suzuki K ，Karita S ，Wakagi T ，Shoun H ，Watanabe T ，Fushinobu S ... -  《-》

Recognition of cello-oligosaccharides by CBM17 from Clostridium cellulovorans : molecular dynamics simulation.

Cao R ，Jin Y ，Xu D 《-》

Differential oligosaccharide recognition by evolutionarily-related beta-1,4 and beta-1,3 glucan-binding modules.

Enzymes active on complex carbohydrate polymers frequently have modular structures in which a catalytic domain is appended to one or more carbohydrate-binding modules (CBMs). Although CBMs have been classified into a number of families based upon sequence, many closely related CBMs are specific for different polysaccharides. In order to provide a structural rationale for the recognition of different polysaccharides by CBMs displaying a conserved fold, we have studied the thermodynamics of binding and three-dimensional structures of the related family 4 CBMs from Cellulomonas fimi Cel9B and Thermotoga maritima Lam16A in complex with their ligands, beta-1,4 and beta-1,3 linked gluco-oligosaccharides, respectively. These two CBMs use a structurally conserved constellation of aromatic and polar amino acid side-chains that interact with sugars in two of the five binding subsites. Differences in the length and conformation of loops in non-conserved regions create binding-site topographies that complement the known solution conformations of their respective ligands. Thermodynamics interpreted in the light of structural information highlights the differential role of water in the interaction of these CBMs with their respective oligosaccharide ligands.

Boraston AB ，Nurizzo D ，Notenboom V ，Ducros V ，Rose DR ，Kilburn DG ，Davies GJ ... -  《JOURNAL OF MOLECULAR BIOLOGY》