Fig. 2

Substrate recognition within the GH128 catalytic domain of CBM6E. a Illustration of the interactions between active-site residues and β-1,3-glucooligosaccharides (GOS). GOS molecules with degrees of polymerization (DPs) of 4 and 5 are depicted in magenta and orange, respectively, representing their positions within the negative- and positive-subsite regions. The insets show expansions of the negative- and positive-subsite regions, as well as the region neighboring the + 5 subsite, respectively. Residues engaged in interactions with GOS are depicted as cyan-colored sticks, while residues neighboring the + 5 subsite, selected for tyrosine substitution, are portrayed as blue-colored sticks. b A polder map contoured at 2σ is presented for GOS with DPs of 4 and 5, observed within the negative and positive-subsite regions, respectively, as derived from the crystal structure of the E168Q inactive mutant of CBM6E-GH128/CBM6 cocrystallized with laminarihexaose. Additionally, CBM6E is represented using an electrostatic potential surface depiction