Figure 7. The accommodation of galactomannan by a family 27 CBM, TmCBM27.

The overall structure surrounding the binding site of TmCBM27 from T. maritima is shown as a ribbon diagram. The three tryptophan side chains comprising the carbohydrate-binding site are shown in grey ‘liquorice’ representation and are numbered. The ligand, G₂M₅, a fragment of galactomannan, is shown in ‘liquorice’ representation with mannose residues in blue and galactose residues in yellow. The uppermost galactose residue in the Figure is clearly bent back over the top of the mannose backbone by Trp²⁸, while the other galactose residue extends comfortably away from the mannose backbone.