Functional and Structural Characterization of the Erythrina fusca Seed Lectin EFusL: A GalNAc-Binding Lectin with Specificity for Tumor-Associated O-Glycans

Abstract

Lectins from the genus Erythrina are predominantly galactoside-binding legume lectins with conserved structural features and established use as glycan-recognition tools. However, several species remain incompletely characterized, including the seed lectin from Erythrina fusca (EFusL). Here, EFusL was isolated by single-step lactose-agarose affinity chromatography and characterized by hemagglutination assays, carbohydrate inhibition, physicochemical stability tests, electrophoresis, mass spectrometry-based sequencing, structural modeling, molecular docking, and toxicity assays. EFusL migrated as a 29–31 kDa glycoprotein and contained approximately 4.3% neutral carbohydrates. Hemagglutination inhibition confirmed a galactoside-directed profile, with lactose, galactose, and N-acetyl-d-galactosamine among the effective inhibitors. EFusL showed maximal hemagglutinating activity at pH 8.0, retained activity up to 40 °C, and displayed reduced activity after EDTA treatment with partial recovery following Ca2+/Mn2+ supplementation. Sequence analysis identified a 249-residue mature lectin highly similar to Erythrina corallodendron and Erythrina cristagalli lectins, including conservation of residues associated with galactoside recognition. Structural modeling supported the canonical β-sandwich legume lectin fold, and docking analyses indicated that EFusL accommodates galactoside ligands through a conserved polar interaction network comparable to related Erythrina lectins and legume lectins in general. Under the tested conditions, EFusL did not induce lethality in Artemia salina and did not significantly affect NHDF viability, although moderate reductions in HeLa and HT-1080 viability were observed under selected concentration- and time-dependent conditions. Together, these results define EFusL as a structurally conserved, galactoside-binding Erythrina lectin with moderate physicochemical stability and limited cell-type-dependent effects in the evaluated models, supporting its classification within the canonical Erythrina lectin group with similar biotechnological potential.