Synthesis and binding analysis of unique AG2 pentasaccharide to human Siglec-2 using NMR techniques

Siglec-2 is a mammalian sialic acid binding protein expressed on B-cell surfaces and is involved in the modulation of B-cell mediated immune response. We synthesized a unique starfish ganglioside, AG2 pentasaccharide Galfβ(1–3)Galpα(1–4)Neu5Acα(2–3)Galpβ(1–4)Glcp, and found that the synthetic pentasaccharide binds to human Siglec-2 by performing 1H NMR experiments. Saturation transfer difference NMR experiments indicated that the C7–C9 side-chain and the acetamide moiety of the central sialic acid residue were located in the binding face of human Siglec-2. We determined the binding epitope of AG2 pentasaccharide to human Siglec-2, as the Galpα(1–4)Neu5Acα(2–3)Galp unit.

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