Discovery and characterization of a novel carbohydrate-binding module: a favorable tool for investigating agarose.

BACKGROUND: Agarose, mainly composed of 3,6-anhydro-α-l-galactopyranose (LA) and ß-d-galactopyranose (G) units, is an important polysaccharide with wide applications in food, biomedical and bioengineering industries. Carbohydrate-binding modules (CBMs) are favorable tools for the investigations of polysaccharides. Few agarose-binding CBMs have been hitherto reported, and their binding specificity is unclear. RESULTS: An unknown domain with a predicted ß-sandwich fold was discovered from a ß-agarase of the marine bacterium Wenyingzhuangia fucanilytica CZ1127T . The expressed protein WfCBM101 could bind to agarose and exhibited relatively weak affinity for porphyran, with no affinity for the other seven examined polysaccharides. The protein binds to the tetrasaccharide (LA-G)2 , but not to the major tetrasaccharide contained in porphyran. The sequence novelty and well-defined binding function of WfCBM101 shed light on a novel CBM family (CBM101). Furthermore, the feasibility of WfCBM101 for visualizing agarose in situ was confirmed. CONCLUSION: A novel CBM, WfCBM101, with a desired specificity for agarose was discovered and characterized, which represents a new CBM family. The CBM could be utilized as a promising tool for studies of agarose. © 2023 Society of Chemical Industry.