Determination of solution conformation of allergenically active pentasaccharitol obtained from sea squirt antigen

Abstract

Pentasaccharitol, GalNAcb1-4(GalNAca1-2Fuca1-3)GlcNAcb1-3GalNAc-ol, termed HPG-b2-N5a, is an allergenically active O-linked oligosaccharitol derived from a sea squirt H-antigen. Concerning the interaction between the allergen and specific IgE, an analysis of the solution conformation of the saccharitol was carried out. 1 H and 13 C NMR assignments for the pentasaccharitol were obtained using 1D-HOHAHA, TOCSY, DEPT135, HSQC and HMBC techniques. The solution conformation was determined using a combination of 2D-NMR ROESY data and distance geometry (DG) calculations in dihedral angle space with the DADAS 90 program. Two conformers, family A (FamA) and family B (FamB), that satisfied almost all the NOE constraints were obtained, and supplemental MD calculations revealed that FamA was in conformational equilibrium whereas FamB was rather flexible. The molecule of HPG-b2-N5a had a layered and not a linear conformation.

A Secondary Structural Element in a Wide Range of Fucosylated Glycoepitopes

“…Typical examples are shown on the right. Structures indicated with an asterics were absent in the database search but were added from two publications . The associated chemical shifts of H5 of Fuc are presented in blue.…”

“…Glycans containing 3FChB are members of the third category that contain α1,3‐fucosylated N ‐glycan cores typically found in plants and invertebrates . Interestingly, several additional motifs that are usually not associated with Lewis antigens were found: α1,3‐fucosylated Lacdi N Ac (LDNF) present in helminths and sea squirt, species‐specific amphibian egg jelly coats with an α1,4‐fucosylation, and fucosylated chondroitin sulfate also display the downfield‐shifted H5 resonance of their Fuc moiety. Moreover, Lewis‐type‐like antigens in which the reducing end of Glc N Ac is substituted by a Glc moiety fulfill the search criterion as well.…”

“…Among the glycans adopting the presented scaffold are physiologically as well as pathophysiologically highly important glycoepitopes: sLe x and 6‐sulfo sLe x , natural ligands of selectins that are involved in leucocyte rolling and homing, sLe x in the zona pellucida is crucial for human fertilization, 6′‐sulfo sLe x is specifically recognized by Siglec‐8, an immunosuppressive co‐receptor present on eosinophiles, whereas 6‐sulfo sLe x is a ligand for Siglec‐9 . In addition, LDNF is a central part of an allergenic sea squirt pentasaccharide and is present in glycans of parasitic helminths, and α1,3‐fucosylated N ‐glycan cores, major allergic determinants of pollen and insect venoms, are found as well. Surprisingly, fucosylated chondroitin sulfate found in crab and sea cucumber that was earlier promoted as selectin antagonist, is also among the stabilized glycoepitopes.…”

“…Structures indicated with an asterics were absent in the databasesearch but were added from two publications. [25,30] The associated chemical shifts of H5 of Fuc are presented in blue. Alight grey background indicates glycans with at hree-dimensional structurei nt he PDB databank.G lycans of which the solution structurew as determined by NMRs pectroscopy werehighlightedi nl ight magenta and framed in red (this work).…”

Characterization of a novel allergenic protein from the octocoral Scleronephthya gracillima (Kuekenthal) that corresponds to a new GFP‐like family named Akane

“…Sea‐squirt ( Styela plicata ), for example, is well known as an allergenic marine animal among workers engaged in oyster shucking, and sea‐squirt oligosaccharides have been identified as allergens that induce allergic reactions such as conjunctivitis and bronchial asthma . The structure of the sea‐squirt oligosaccharide allergen epitopes was determined using two‐dimensional (2D) nuclear magnetic resonance (NMR) methods and a molecular dynamics simulation method …”