Homology between jacalin and artocarpin from jackfruit (Artocarpus integrifolia) seeds. Partial sequence and preliminary crystallographic studies of artocarpin

Abstract

Jacalin and artocarpin, the two lectins from jackfruit (Artocarpus integrifolia) seeds, have different physicochemical properties and carbohydrate-binding specificities. However, comparison of the partial amino-acid sequence of artocarpin with the known sequence of jacalin indicates close to 50% sequence identity. Artocarpin crystallizes in two forms, both monoclinic P2₁, with one and two tetramic molecules, respectively, in the asymmetric units of form I (a = 69.9, b = 73.7, c = 60.6 Å and β = 95.1°) and form II (a = 87.6, b = 72.2, c = 92.6 Å and β = 101.1°). Both the crystal structures have been solved by the molecular replacement method using the known structure of jacalin as the search model and one of them partially refined, confirming that the two lectins are indeed homologous.