Comparative epitope mapping with saturation transfer difference NMR of sialyl Lewis(a) compounds and derivatives bound to a monoclonal antibody.
The monoclonal antibody GSLA-2 recognizes the sialyl Lewis(a) (sLe(a)) epitope, which has an increased occurrence on mucin type glycoproteins of patients with colorectal carcinoma. GSLA-2 is therefore used in tumor diagnosis. To advance the understanding of this highly specific molecular recognition reaction, we have analyzed the binding epitope of sLe(a) at atomic resolution using saturation transfer difference NMR. To compare, the binding epitopes of sialyl Lewis(x) (sLe(x)) and of four synthetic derivatives of sLe(a) were explored. Surface plasmon resonance experiments furnished thermodynamic and kinetic data. It is observed that all pyranose rings of sLe(a) are in contact with the protein surface, with the neuramic acid residue receiving the largest fraction of saturation transfer. In contrast, sLe(x) binds very weakly, though specifically to GSLA-2, with a different binding epitope. This study provides a comprehensive picture of the recognition sLe(a) and explains the exquisite specificity of the antibody.
Herfurth
Lars
L
Institute of Chemistry, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany.
Ernst
Beat
B
Wagner
Beatrice
B
Ricklin
Daniel
D
Strasser
Daniel S
DS
Magnani
John L
JL
Benie
Andrew J
AJ
Peters
Thomas
T
D000911:Antibodies, Monoclonal / Q000737:chemistry*; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000737:chemistry*; D001665:Binding Sites; D018395:CA-19-9 Antigen; D002240:Carbohydrate Sequence; D018604:Epitope Mapping; D005732:Gangliosides / Q000737:chemistry*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry; D000080506:Sialyl Lewis X Antigen; D020349:Surface Plasmon Resonance; D013816:Thermodynamics
D000911:Antibodies, Monoclonal; D015295:Antigens, Tumor-Associated, Carbohydrate; D018395:CA-19-9 Antigen; D005732:Gangliosides; D009844:Oligosaccharides; D000080506:Sialyl Lewis X Antigen; C064564:sialyl Le(a) ganglioside