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A small grid of conditions has been developed for co-crystallization of the plant lectin concanavalin A (conA) and polysaccharides. Crystals have been obtained of complexes of conA with α1-2 mannobiose, 1-methyl α1-2 mannobiose, fructose, a trisaccharide and a pentasaccharide. The crystals diffract to resolutions of 1.75-2.7 Å using a copper rotating-anode source. The crystals are grown in the presence of polyethylene glycol 6K [10-20%(w/v)] at around pH 6.0. Optimization for each particular carbohydrate requires small adjustments in the conditions; however, all complexes give some crystalline precipitate in this limited grid. The α1-2 mannobiose complex crystals diffract to 1.75 Å with space group I222 and cell dimensions a: 91.7, b = 86.8, c = 66.6 Å. One monomer is present in the asymmetric unit. The 1-methyl α1-2 mannobioside complex crystallizes in space group P212121, cell dimensions a = 119.7, b = 119.7, c= 68.9 Å and diffract to 2.75 Å. One tetramer is present in the asymmetric unit. Two crystal forms of the conA-fructose complex have been obtained. The first has space group P212121, cell dimensions a = 121.7, b = 119.9, c = 67.3 Å with a tetramer in the asymmetric unit and diffracts to 2.6 Å. The second crystallizes in space group C2221, cell dimensions a = 103.3, b = 117.9, c = 254.3 with two dimers in the asymmetric unit and diffracts to 2.42 Å. Structures and crystallization of the trisaccharide-conA and pentasaccharide-conA complexes have already been reported. In all complexes, the protein is found as a tetramer, although varying combinations of non-crystallographic and crystallographic symmetry are involved in generating the tetramer. The precise packing of the tetramer varies from crystal to crystal and it is likely that this variability facilitates crystallization.

Original publication

DOI

10.1107/S0907444998008919

Type

Journal article

Journal

Acta Crystallographica Section D: Biological Crystallography

Publication Date

01/01/1999

Volume

55

Pages

353 - 355