Structural and functional variation of chitin-binding domains of a lytic polysaccharide monooxygenase from Cellvibrio japonicus
Eva Madland, Zarah Forsberg, Yong Wang, Kresten Lindorff‐Larsen, Axel Niebisch, Jan Modregger, Vincent G. H. Eijsink, Finn L. Aachmann, Gastón Courtade
Abstract
values in the micromolar range, CjCBM73 has higher affinity for chitin than CjCBM5. Furthermore, NMR titration experiments showed that CjCBM5 binds soluble chitohexaose, whereas no binding of CjCBM73 to this chitooligosaccharide was detected. These functional differences correlate with distinctly different arrangements of three conserved aromatic amino acids involved in substrate binding. In CjCBM5, these residues show a linear arrangement that seems compatible with the experimentally observed affinity for single chitin chains. On the other hand, the arrangement of these residues in CjCBM73 suggests a wider binding surface that may interact with several chitin chains. Taken together, these results provide insight into natural variation among related chitin-binding CBMs and the possible functional implications of such variation.