Algal lectin binding to core (alpha 1-6) fucosylated N-glycans: Structural basis for specificity and production of recombinant protein

作者：do Nascimento Antonia S F; Serna Sonia; Beloqui Ana; Arda Ana; Sampaio Alexandre H; Walcher Janika; Ott Dimitri; Unverzagt Carlo; Reichardt Niels Christian; Jimenez Barbero Jesus; Nascimento Kyria S; Imberty Anne^*; Cavada Benildo S; Varrot Annabelle

来源：Glycobiology, 2015, 25(6): 607-616.

DOI：10.1093/glycob/cwv002

• algal lectin
• Bryothamnion triquetrum
• carbohydrate-binding specificity
• core alpha 1
• 6-fucose

We determined the specificity of BTL, a lectin from the red marine alga Bryothamnion triquetrum, toward fucosylated oligosaccharides. BTL showed a strict specificity for the core alpha 1,6-fucosylation, which is an important marker for cancerogenesis and quality control of therapeutical antibodies. The double fucosylation alpha 1,6 and alpha 1,3 was also recognized, but the binding was totally abolished in the sole presence of the alpha 1,3-fucosylation. A more detailed analysis of the specificity of BTL showed a preference for bi- and tri-antennary nonbisected N-glycans. Sialylation or fucosylation at the nonreducing end of N-glycans did not affect the recognition by the lectin. BTL displayed a strong affinity for a core alpha 1,6-fucosylated octasaccharide with a K-d of 12 mu M by titration microcalorimetry. The structural characterization of the interaction between BTL and the octasaccharide was obtained by STD-NMR. It demonstrated an extended epitope for recognition that includes the fucose residue, the distal GlcNAc and one mannose residue. Recombinant rBTL was obtained in Escherichia coli and characterized. Its binding properties for carbohydrates were studied using hemagglutination tests and glycan array analysis. rBTL was able to agglutinate rabbit erythrocytes with strong hemagglutination activity only after treatment with papain and trypsin, indicating that its ligands were not directly accessible at the cell surface. The hemagglutinating properties of rBTL confirm the correct folding and functional state of the protein. The results show BTL as a potent candidate for cancer diagnosis and as a reagent for the preparation and quality control of antibodies lacking core alpha 1,6-fucosylated N-glycans.

• 出版日期2015-6