Fig. 6.

The active site in Op5Man5. (A) Op5Man5 with a mannotriose molecule modeled in the active site with the three mannose units occupying subsites −1, +1 and + 2. Relevant side chains that are suitably positioned to interact with the substrate are shown. (B) Overlay of the TIM barrel in Op5Man5 (yellow), RmMan5B (light blue; PDB code 4LYQ) and TfMan (green; PDB code 3MAN). The mannotriose molecule in the exo-β-1,4-mannosidase RmMan5B occupies subsites –1 to + 2, and in the endo-β-mannanase TfMan, mannotriose is bound at subsites –2 to –4. The loops forming the steric block that closes off the negative subsites in the exo-acting enzymes Op5Man5 and RmMan5B are indicated by a gray circle. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)