Importance of Hydrophobic and Polar Residues in Ligand Binding in the Family 15 Carbohydrate-Binding Module from Cellvibrio japonicus Xyn10C

• DOI: 10.1021/bi0347510
• Publication Date: 2003-08-05T04:49:16Z
• Authors: Gavin Pell; Michael P. Willia...; Christopher Walters; Haomao Du; Harry J. Gilbert; David N. Bolam
• Keywords: Carbohydrate-binding module

Modular glycoside hydrolases that degrade the plant cell wall often contain noncatalytic carbohydrate-binding modules (CBMs) interact with specific polysaccharides within this complex macromolecule. CBMs, by bringing appended catalytic module into intimate and prolonged association substrate, increase rate at which these enzymes are able to hydrolyze glycosidic bonds. Recently, crystal structure of family 15 CBM (CBM15) from Cellvibrio japonicus (formerly Pseudomonas cellulosa) Xyn10C was determined in ligand xylopentaose. In report we have used a rational design approach, informed CBM15−ligand complex, probe importance hydrophobic stacking interactions both direct water-mediated hydrogen bonds binding protein xylan xylohexaose. The data show replacing either Trp 171 or 186, stack against xylose residues n + 2 xylopentaose, alanine abolished binding. Similarly, Asn 106, Gln 171, 217, make greatly reduced affinity for its saccharide ligands. By contrast, disrupting between CBM15 xylopentaose introducing mutations S108A, Q167A, Q221A, K223A had little effect on These indicate binds xylooligosaccharides via same provide clear evidence key determinant type B CBM. generic is discussed.