Crystallization and preliminary X-ray diffraction studies of frutalin, an α-D-galactose-specific lectin from Artocarpus incisa seeds

Abstract

Frutalin is an α-D-galactose-specific carbohydrate-binding glycoprotein with antitumour properties and is a powerful tool for tumour biomarker discovery. The crystallization and preliminary X-ray diffraction analysis of this lectin, which was isolated from Artocarpus incisa seeds, are reported here. Frutalin was purified and submitted to mass-spectrometric analysis. Diverse masses at approximately 16 kDa were observed in the deconvoluted spectra, which support the presence of isoforms. The best frutalin crystals were grown within a week in 0.1 M citric acid pH 3.5 which contained 25% PEG 3350 as a precipitant at 293 K, and diffracted to a maximum resolution of 1.81 Å. The monoclinic crystals belonged to space group I2, with unit-cell parameters a = 76.17, b = 74.56, c = 118.98 Å, β = 96.56°. A molecular-replacement solution was obtained which indicated the presence of four monomers per asymmetric unit. Crystallographic refinement of the structure is in progress.

Keywords: Artocarpus incisa; frutalin; jacalin lectin-related family.

Figure 1

Intact deconvoluted mass spectrum of FTL showing masses around 16 kDa. Inset, SDS–PAGE showing two bands between 20 and 14 kDa. Lane M, molecular-mass markers (labelled in kDa); lane 2, FTL.

Figure 2

Crystals of FTL grown in citric acid pH 3.5 containing PEG 3350 as a precipitant.

Figure 3

Diffraction pattern of an FTL crystal to 1.81 Å resolution.