Xanthosoma sagittifolium Tubers Contain a Lectin with Two Different Types of Carbohydrate-binding Sites

• Published in: The Journal of biological chemistry Vol. 274; no. 47; pp. 33300 - 33305
• Main Authors: Mo, Hanqing, Rice, Kevin G., Evers, David L., Winter, Harry C., Peumans, Willy J., Van Damme, Els J.M., Goldstein, Irwin J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19.11.1999; American Society for Biochemistry and Molecular Biology
• Subjects: amino acid sequences; binding sites; Carbohydrate Sequence; carbohydrates; chemical structure; lectins; Lectins - chemistry; Lectins - isolation & purification; mannans; Molecular Sequence Data; Molecular Weight; n-lined carbohydrates; oligomannoses; oligosaccharides; Plant Lectins; Plants - chemistry; Precipitin Tests; Protein Conformation; tubers; Xanthosoma sagittifolium
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.47.33300

An unusual lectin possessing two distinctly different types of carbohydrate-combining sites was purified from tubers of Xanthosoma sagittifolium L. by consecutive passage through two affinity columns, i.e.asialofetuin-Sepharose and invertase-Sepharose. SDS-polyacrylamide gel electrophoresis, N-terminal amino acid sequencing, and gel filtration chromatography of the purified lectin showed that theX. sagittifolium lectin is a heterotetrameric protein composed of four 12-kDa subunits (α2β2) linked by noncovalent bonds. The results obtained by quantitative precipitation and hapten inhibition assays revealed that the lectin has two different types of carbohydrate-combining sites: one type for oligomannoses, which preferentially binds to a cluster of nonreducing terminal α1,3-linked mannosyl residues, and the other type for complex N-linked carbohydrates, which best accommodates a non-sialylated, triantennary oligosaccharide withN-acetyllactosamine (i.e. Galβ1,4GlcNAc-) or lacto-N-biose (i.e. Galβ1,3GlcNAc-) groups at its three nonreducing termini.