Epitope mapping of sialyl Lewis(x) bound to E-selectin using saturation transfer difference NMR experiments.
A complex between sialyl Lewisx (alpha-D-Neu5Ac-[2-->3]- beta-D-Gal-[1-->4]-[alpha-L-Fuc-(1-->3)]-beta-D-GlcNAc-O-[CH2]8 COOMe) and E-selectin was studied using saturation transfer difference (STD) nuclear magnetic resonance (NMR) experiments. These experiments allow the identification of the binding epitope of a ligand at atomic resolution. A semiquantitative analysis of STD total correlation spectroscopy spectra provides clear evidence that the galactose residue receives the largest saturation transfer. The protons H4 and H6 of the galactose residue are in especially close contact to the amino acids of the E-selectin binding pocket. The fucose residue also receives a significant saturation transfer. The GlcNAc and Neu5Ac residues, with the exception of H3 and H3' of Neu5Ac, were found to interact weakly with the protein surface. These findings are in excellent agreement with a recently published X-ray structure and with the earlier findings from syntheses and activity assays. To further characterize the binding pocket of E-selectin, an inhibitory peptide, Ac-TWDQLWDLMK-CONH2, was synthesized and the binding to E-selectin studied utilizing transfer nuclear Overhauser effect spectroscopy (trNOESY) experiments. Finally, competitive trNOESY experiments were performed, showing that the synthetic peptide is a competitive inhibitor of sialyl Lewisx.
Rinnbauer
Meike
M
Institute of Chemistry, University of Luebeck, Ratzeburger Allee 160, D-23538 Luebeck, Germany.
Ernst
Beat
B
Wagner
Bea
B
Magnani
John
J
Benie
Andrew J
AJ
Peters
Thomas
T
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D019040:E-Selectin / Q000737:chemistry* / Q000378:metabolism*; D018604:Epitope Mapping / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism*; D019151:Peptide Library; D011485:Protein Binding; D000080506:Sialyl Lewis X Antigen
D019040:E-Selectin; D009844:Oligosaccharides; D019151:Peptide Library; D000080506:Sialyl Lewis X Antigen