Concanavalin A crystallized in complex with the trisaccharide 3,6-di-O-methyl-(α-D-mannopyranosyl)-α-D-mannopyranoside

Concanavalin A was co-crystallized in two crystal forms with 3,6-di-O-methyl- (α-D-mannopyranosyl) α- D-mannopyranoside, which is primarily responsible for the high-affinity binding of N-linked carbohydrates to concanavalin A. Both crystal forms have space group P2₁ and contain a complete concanavalin A tetramer in the asymmetric unit. Form A was crystallized using polyethylene glycol methyl ether as the precipitant and has unit-cell dimensions a = 59.83, b = 64.84 and c = 125.92 Å, β = 93.87°. Form B was obtained using phosphate as the precipitant and has unit-cell dimensions a = 81.94, b = 66.75 and c = 108.92 Å, β = 97.58°. Form B was stable in the X-ray beam for several days and diffracted to 3.15 Å resolution. Form A crystals could not withstand X-ray radiation at room temperature, but produced high-quality data under cryogenic conditions. The latter are suitable for a 2.3 Å resolution structure determination by molecular replacement.