Engineering of recombinant Wisteria floribunda agglutinin specifically binding to GalNAcβ1,4GlcNAc (LacdiNAc).

Wisteria floribunda agglutinin (WFA) is a useful probe for distinguishing glycan structural alterations in diseases such as intrahepatic bile duct carcinoma and hepatic fibrosis; however, the gene encoding WFA has not been identified. Here, we identified the gene encoding WFA, and recombinant WFA was expressed in Escherichia coli and purified. The natural cDNA sequence obtained from wisteria seeds contained an open reading frame of 861 nucleotides encoding a WFA precursor, which included a hydrophobic signal peptide at the N-terminus, a propeptide at the C-terminus and a single cysteine (Cys) residue for dimer formation. We characterized the natural and recombinant WFA by the glycoconjugate microarray and frontal affinity chromatography. Recombinant WFA exhibited glycan binding specificity similar to that of natural WFA: both bound to Gal- and GalNAc-terminated glycans. Moreover, the engineered WFA with an amino acid substitution in Cys-272 yielded a recombinant monomeric lectin with limited binding specificity but wild-type affinity for GalNAc-terminated glycans, specifically GalNAcβ1,4GlcNAc. Thus, this engineered lectin may be applied to highly sensitive biomarker detection.