Characterization of a diagnostic Fab fragment binding trimeric Lewis X.
Lewis X trisaccharides normally function as essential cell-cell interaction mediators. However, oligomers of Lewis X trisaccharides expressed by the parasite Schistosoma mansoni seem to be related to its evasion of the immune response of its human host. Here we show that monoclonal antibody 54-5C10-A, which is used to diagnose schistosomiasis in humans, interacts with oligomers of at least three Lewis X trisaccharides, but not with monomeric Lewis X. We describe the sequence and the 2.5 A crystal structure of its Fab fragment and infer a possible mode of binding of the polymeric Lewis X from docking studies. Our studies indicate a radically different mode of binding compared to Fab 291-2G3-A, which is specific for monomeric Lewis X, thus providing a structural explanation of the diagnostic success of 54-5C10-A.
de Geus
Daniël C
DC
Leiden University, The Netherlands. d.de.geus@chem.leidenuniv.nl
van Roon
Anne-Marie M
AM
Thomassen
Ellen A J
EA
Hokke
Cornelis H
CH
Deelder
André M
AM
Abrahams
Jan Pieter
JP
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry* / Q000276:immunology; D016256:Lewis X Antigen / Q000031:analogs & derivatives; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment; D020349:Surface Plasmon Resonance; D014312:Trisaccharides / Q000737:chemistry* / Q000276:immunology*
D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; D016256:Lewis X Antigen; D014312:Trisaccharides; C110530:galactosyl-(1,4)-fucopyranosyl-(1,3)-N-acetylglucosamine