ricin B-type lectin domain, beta-trefoil fold, found in Boletus edulis lectin (BEL), Laetiporus sulphureus lectin (LSL) and similar proteins
BEL has potent anti-proliferative effects on human cancer cells. It functions as a homodimer and each protomer folds as a beta-trefoil. The BEL beta-trefoil binds galactose and other galactose-containing carbohydrates. LSL is a lectin that exhibits hemolytic and hemagglutinating activities. It functions as a hexamer. Its monomeric protein consists of two distinct modules: an N-terminal beta-trefoil lectin module (LSL150) and a C-terminal membrane pore-forming module (PFM). All members of this subfamily contain a ricin B-type lectin domain with a beta-trefoil fold, which is characterized by 12 beta strands folded into three similar trefoil subdomains (called alpha, beta, and gamma, respectively) associated to give an overall structure with pseudo-3-fold symmetry. Each subdomain may contain a potential sugar-binding site. Due to the lack of an aromatic residue, the sugar binding within alpha-site of LSL150 might be absent.
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