Interaction between the CBM of Cel9A from Thermobifida fusca and cellulose fibers

Molecular docking and molecular dynamics (MD) simulations were used to investigate the binding of a cellodextrin chain in a crystal-like conformation to the carbohydrate-binding module (CBM) of Cel9A from Thermobifida fusca. The fiber was found to bind to the CBM in a single and well-defined configuration in-line with the catalytic cleft, supporting the hypothesis that this CBM plays a role in the catalysis by feeding the catalytic domain (CD) with a polysaccharide chain. The results also expand the current known list of residues involved in the binding. The polysaccharide-protein attachment is shown to be mediated by five amine/amide-containing residues. E478 and E559 were found not to interact directly with the sugar chain; instead they seem to be responsible to stabilize the binding motif via hydrogen bonds.