A Triclinic Crystal Form of the Lectin Concanavalin A

The molecular structure of a triclinic crystal form of concanavalin A has been refined at 2.4 A resolution. The crystals have unit cell dimensions a = 78.8 A, b = 79.3 A, c = 133.3 A, alpha = 97.1degrees, beta = 90.2degrees, and gamma = 97.5degrees and contain two tetramers per asymmetric unit each with approximate 222 symmetry. The final crystallographic R-factor is 0.205 and the free-R-factor is 0.265 in the resolution range 6.0 to 2.4 A. The conformation of the tetramer is more similar to that found in concanavalin A saccharide complexes than in the previously reported I222 crystal form of uncomplexed concanavalin A. A comparison of the molecular packing between the two crystal forms shows a more open arrangement with large solvent channels through the crystal.