Evidence for the extended helical nature of polysaccharide epitopes. The 2.8 A resolution structure and thermodynamics of ligand binding of an antigen binding fragment specific for alpha-(2-->8)-polysialic acid.Evans, S.V., Sigurskjold, B.W., Jennings, H.J., Brisson, J.R., To, R., Tse, W.C., Altman, E., Frosch, M., Weisgerber, C., Kratzin, H.D., Klebert, S., Vaesen, M., Bitter-Suermann, D., Rose, D.R., Young, N.M., Bundle, D.R.
(1995) Biochemistry 34: 6737-6744
- PubMed: 7538787
- PubMed Abstract:
- Helical Epitope of the Group B Meningococcal Alpha(2->8)-Linked Sialic Acid Polysaccharide
Brisson, J.-R.,Baumann, H.,Imberty, A.,Perez, S.,Jennings, H.J.
(1992) Biochemistry 31: 4996
The antigen binding fragment from an IgG2a kappa murine monoclonal antibody with specificity for alpha-(2-->8)-linked sialic acid polymers has been prepared and crystallized in the absence of hapten. Crystals were grown by vapor diffusion equilibrium ...
The antigen binding fragment from an IgG2a kappa murine monoclonal antibody with specificity for alpha-(2-->8)-linked sialic acid polymers has been prepared and crystallized in the absence of hapten. Crystals were grown by vapor diffusion equilibrium with 16-18% polyethylene glycol 4000 solutions. The structure was solved by molecular replacement methods and refined to a conventional R factor of 0.164 for data to 2.8 A. The binding site is observed to display a shape and distribution of charges that is complementary to that of the predicted conformation of the oligosaccharide epitope. A thermodynamic description of ligand binding has been compiled for oligosaccharides ranging in length from 9 to 41 residues, and the data for the largest ligand has been used in a novel way to estimate the size of the antigen binding site. A model of antigen binding is presented that satisfies this thermodynamic data, as well as a previously reported requirement of conformational specificity of the oligosaccharide. X-ray crystallographic and thermodynamic evidence are consistent with a binding site that accommodates at least eight sialic acid residues.
Institute for Biological Sciences, National Research Council of Canada, Ottawa.