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 ( P2 1, a = 59·4 A ̊ , b = 83·3 A ̊ , c = 63·5 A ̊ , β = 107·7°; C2, a = 106·1, A ̊ , b = 53·9 A ̊ , c = 128·0 A ̊ , β = 95·0 A ̊ ) and one orthorhombic ( C222 1, a = 98·1 A ̊ , b = 67·3 A ̊ , c = 95·1 A ̊ ) were grown with 2-methylpentan-2,4-diol (MPD) as the precipitant while the fourth, an hexagonal from ( P6 122, a = b = 129·6 A ̊ , c = 157·9 A ̊ ), 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.