The alpha- and beta-subunits of the jacalins are cleavage products from a 17-kDa precursor

The jacalins of three Artocarpus species were purified by affinity chromatography on a desialylated mucin-CNBr-Sepharose 4B column. The beta-chains and the 14 kDa alpha-chains were separated by high pressure liquid chromatography and the 17 kDa chains by preparative electrophoresis. The 17 kDa and 14 kDa chains had a similar highly conserved N-terminal sequence. The beta-chains were different for the three species and Artocarpus champeden contained two different beta-chains. CNBr cleavage of the 17 kDa polypeptide of Artocarpus tonkinensis yielded one peptide more than the 14 kDa. The N-terminal sequence of this fragment was similar to that of the beta-chain proving that this chain results from a proteolytic cleavage at the C-terminus of the 17 kDa peptide. The large heterogeneity of the beta-chains of jacalins from different species could be used as a marker for evolutionary studies on the Artocarpus family.