Preparation and X-ray characterization of four new crystal forms of jacalin, a lectin from Artocarpus integrifolia

Abstract

Four new crystal forms of the anti-T lectin from jackfruit (Artocarpus integrifolia) have been prepared and characterized. Three of them, two monoclinic (P2₁, A = 59·4 Å, B = 83·3 Å, C = 63·5 Å, β = 107·7°; C2, A = 106·1,Å, B = 53·9 Å, C = 128·0 Å, β = 95·0 Å) and one orthorhombic (C222₁, A = 98·1 Å, B = 67·3 Å, C = 95·1 Å) were grown with 2-methylpentan-2,4-diol (MPD) as the precipitant while the fourth, an hexagonal from (P6₁22, A = b = 129·6 Å, C = 157·9 Å), was obtained in the presence of methyl-ga-D-galactopyranoside with polyethylene glycol 4000 as the precipitant. The reported relative molecular mass (M_r) of the lectin was found to be inconsistent with the solvent content of the crystals estimated using measured densities. The M_r was redetermined using size-exclusion chromatography in the presence of methyl-α-D-galactopyranoside and Ferguson-plot analysis of mobilities in polyacrylamide gel electrophoresis. The redetermined M_r (66,000) is consistent with the measured crystal densities. The orthorhombic and the hexagonal forms, which have one half molecule and one molecule, respectively, in the asymmetric unit, are suitable for high-resolution X-ray analysis.