Structural insights into antibody recognition of mycobacterial polysaccharides.Murase, T., Zheng, R.B., Joe, M., Bai, Y., Marcus, S.L., Lowary, T.L., Ng, K.K.
(2009) J Mol Biol 392: 381-392
- PubMed: 19577573
- DOI: https://doi.org/10.1016/j.jmb.2009.06.074
- Primary Citation of Related Structures:
3HNS, 3HNT, 3HNV
- PubMed Abstract:
Mycobacteria are major human pathogens responsible for such serious and widespread diseases as tuberculosis and leprosy. Among the evolutionary adaptations essential for pathogenicity in mycobacteria is a complex carbohydrate-rich cell-wall structure that contains as a major immunomodulatory molecule the polysaccharide lipoarabinomannan (LAM). We report here crystal structures of three fragments from the non-reducing termini of LAM in complex with a murine antibody Fab fragment (CS-35Fab). These structures reveal for the first time the three-dimensional structures of key components of LAM and the molecular basis of LAM recognition at between 1.8- and 2.0-A resolution. The antigen-binding site of CS-35Fab forms three binding pockets that show a high degree of complementarity to the reducing end, the branch point and one of the non-reducing ends of the Y-shaped hexasaccharide moiety found at most of the non-reducing termini of LAM. Structures of CS-35Fab bound to two additional tetrasaccharides confirm the general mode of binding seen in the hexasaccharide and indicate how different parts of LAM are recognized. Altogether, these structures provide a rational basis for understanding the overall architecture of LAM and identify the key elements of an epitope that may be exploited for the development of novel and more effective anti-mycobacterial vaccines. Moreover, this study represents the first high-resolution X-ray crystallographic investigation of oligofuranoside-protein recognition.
Alberta Ingenuity Centre for Carbohydrate Science, University of Calgary, Calgary, Alberta, Canada.