RoSBD belonging to CBM family 21 with a molecular weight of 11.7 kDa, and is classified as a member of Type B glycan chain-binding CBM. Ro-SBD consists of eight β-strands forming two β-sheets with a distorted barrel structure. RoSBD possesses two ligand-binding sites, where hydrophobic interactions between the sugar rings and aromatic residues on RoSBD surface play crucial roles in ligand binding. RoSBD has been demonstrated to be effectively adsorbed onto raw starch and other soluble oligosaccharides. The binding of RoSBD has been identified to be stable over a wide range of conditions; hence it can be eluted from starch or amylose resin with elevated pH. RoSBD has been developed as a rapid and economic recombinant protein purification system depending on pH.
Eosinophil cationic protein (ECP) is secreted by activated granular eosinophilic leukocytes and is the best known protein marker for asthma and other inflammatory diseases. ECP belongs to human ribonuclease (RNase) A superfamily and is also named as RNase 3. It is a single polypeptide composed of 133 amino acids with three α-helices and six beta sheets. Our studies revealed that the cytotoxic activity of ECP toward Beas-2B human bronchial epithelial cells depended on binding to the cell surface glycosaminoglycan (GAGs), specifically heparan sulfate proteoglycans (HSPGs), followed by endocytosis. We have demonstrated the key residues in heparin binding motif for cell binding, and discovered multiple functions of ECP, which facilitates understanding of molecular interaction between ECP and cell surface and cell membrane components, as well as cytotoxicity mechanisms of ECP.