Carbohydrate-binding modules from family 11:: Understanding the binding mode of polysaccharides

This article focuses on the molecular determinants that drive the binding and recognition of polysaccharides to the carbohydrate-binding modules (CBMs) from family 11. The CBMs are noncatalytic modules of a high-hierarchy multisubunit complex called cellulosome, which are known to be crucial for the efficient degradation of polysaccharides. Their function and behavior has not yet been fully clarified, and taking into account the bioeconomical interest in this subject it has become a challenging research problem. Our computational results point to the fact that the binding interface of the CBM11 can bind only one single polysaccharide chain, which is in agreement with other CBMs from type B. The central binding site has affinity for polysaccharides with more than four subunits, and there are four main residues that have a central role in this interaction: Asp99, Arg126, Asp128, and Asp146. Furthermore, there are three tyrosine residues, Tyr22, Tyr53, and Tyr129 that are crucial for the guiding and packing of the polysaccharide to the charged regions. In this article, we have also compared the structure of the CBM11 with other CBMs families from type B and found many similarities, which suggest similar binding activities and functions. (c) 2008 Wiley Periodicals, Inc.