Preliminary Crystallographic Analysis of a Fab Specific for the O-antigen of Shigella flexneri Cell Surface Lipopolysaccharide with and without Bound Saccharides

The Fab a monoclonal anti-carbohydrate antibody, SYA/J6 (IgG 3, κ, murine), raised against the O-polysaccharide antigen of the cell surface lipopolysaccharide of variant Y Shigella flexneri, a Gram negative bacterium, has been crystallized in the unliganded form and in complex with tri- and pentasaccharide antigens. The three crystal forms belong to the tetragonal space group P4 32 12, or P 4 12 12, with very similar unit cell dimensions and an asymmetric unit that contains one molecule of about 50,000 Daltons, and a fourth crystal form belongs to monoclinic space group P2 1, that contains four molecules of Fab in an asymmetric unit. Whereas diffractions of these crystals on an area detector-rotating anode system extend to only about 3·5 Å resolution, those measured using an imaging plate and synchrotron radiation at the Photon Factory facility extend to 2·5 Å