A Simple Method for Determining Specificity of Carbohydrate-Binding Modules for Purified and Crude Insoluble Polysaccharide Substrates

Experimental identification of carbohydrate-binding modules (CBM) and determination of ligand specificity of each CBM are complementary and compulsory steps for their characterization. Some CBMs are very specific for their primary substrate (e.g., cellulose), whereas others are relatively promiscuous or nonspecific in their substrate preference. Here we describe a simple procedure based on in-tube adsorption of a CBM to various insoluble polysaccharides, followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) for determining the distribution of the CBM between the bound and unbound fractions. This technique enables qualitative assessment of the binding strength and ligand specificity for each CBM.