Solution Structure, Dynamics and Binding Studies of a Family 11 Carbohydrate-Binding Module from Clostridium thermocellum (CtCBM11).
Related Articles Solution Structure, Dynamics and Binding Studies of a Family 11 Carbohydrate-Binding Module from Clostridium thermocellum (CtCBM11).
Biochem J. 2013 Jan 29;
Authors: Viegas A, Sardinha J, Freire F, Duarte DF, Carvalho AL, Fontes CM, Romão MJ, Macedo AL, Cabrita EJ
Abstract
Non-catalytic cellulosomal carbohydrate-binding modules (CBMs) are responsible for increasing the catalytic efficiency of cellulosic enzymes by selectively putting the substrate (a wide range of poly- and oligosaccharides) and enzyme into close contact. In the present work we carried out an atomistic rationalization of the molecular determinants of ligand specificity of a family 11 CBM from thermophilic C. thermocellum (CtCBM11), based on a NMR and
molecular modeling approach. We have determined the NMR solution structure of CtCBM11 at 25 and 50 ºC and derived information on the residues of the protein involved in ligand recognition and on the influence of the length of the saccharide chain on binding. We obtained models of the CtCBM11/cellohexaose and CtCBM11/cellotetraose complexes by docking in accordance with the NMR experimental data. Specific ligand/protein CH-? and Van der Waals interactions were found to be determinant for the stability of the complexes and for defining specificity. Using the order parameters derived from backbone dynamics analysis in the presence and absence of ligand and at 25 and 50 ºC, we determined that the protein's backbone conformational entropy is slightly positive. This data in combination with the negative binding entropy calculated from ITC studies supports a selection mechanism where a rigid protein selects a defined oligosaccharide conformation.
PMID: 23356867 [PubMed - as supplied by publisher]
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