Structural insights into parallel strategies for germline antibody recognition of lipopolysaccharide from Chlamydia.Evans, D.W., Muller-Loennies, S., Brooks, C.L., Brade, L., Kosma, P., Brade, H., Evans, S.V.
(2011) Glycobiology 21: 1049-1059
- PubMed: 21543444
- DOI: 10.1093/glycob/cwr041
- Primary Citation of Related Structures:
- PubMed Abstract:
The structure of the antigen-binding fragment from the monoclonal antibody S64-4 in complex with a pentasaccharide bisphosphate fragment from chlamydial lipopolysaccharide has been determined by x-ray diffraction to 2.6 Å resolution. Like the well-ch ...
The structure of the antigen-binding fragment from the monoclonal antibody S64-4 in complex with a pentasaccharide bisphosphate fragment from chlamydial lipopolysaccharide has been determined by x-ray diffraction to 2.6 Å resolution. Like the well-characterized antibody S25-2, S64-4 displays a pocket formed by the residues of germline sequence corresponding to the heavy and light chain V gene segments that binds the terminal Kdo residue of the antigen; however, although S64-4 shares the same heavy chain V gene segment as S25-2, it has a different light chain V gene segment. The new light chain V gene segment codes for a combining site that displays greater affinity, different specificity, and allows a novel antigen conformation that brings a greater number of antigen residues into the combining site than possible in S25-2. Further, while antibodies in the S25-2 family use complementarity determining region (CDR) H3 to discriminate among antigens, S64-4 achieves its specificity via the new light chain V gene segment and resulting change in antigen conformation. These structures reveal an intriguing parallel strategy where two different combinations of germline-coded V gene segments can act as starting points for the generation of germline antibodies against chlamydial antigens and show how anti-carbohydrate antibodies can exploit the conformational flexibility of this class of antigens to achieve high affinity and specificity independently of CDR H3.
Department of Biochemistry and Microbiology, University of Victoria, PO Box 3055 STN CSC, Victoria, BC, Canada V8P 3P6.