THE ISOLATION AND CHARACTERIZATION OF JACALIN [ARTOCARPUS-HETEROPHYLLUS (JACKFRUIT) LECTIN] BASED ON ITS CHARGE PROPERTIES

Jackfruit extracts contain a protein termed jacalin which possesses di verse biological properties. A detailed analysis of its charge propert ies has been lacking. The present investigation was initiated to study isoelectric properties of jacalin in detail and to isolate a single i soform of jacalin. Jacalin was isolated from jackfruit extracts by aff inity chromatography on immunoglobulin-ii immobilised to Sepharose 4B. Various techniques such as ion-exchange chromatography, isoelectric f ocusing (IEF) on polyacrylamide gels and preparative liquid IEF, with the Rotofor cell were used. When analysed by IEF on thin layer polyacr ylamide gels, jacalin was resolved into 35 bands over a pH range of 5. 0-8.5. Upon SDS-PAGE in the second dimension all these charge species gave rise to only two-bands at 12 and 15.4 kDa. The lectin was mostly eluted with 50 and 100 mM sodium chloride when jackfruit extracts were fractionated on an anion-exchange column of DEAE-cellulose. In a sing le 6 hour run by preparative IEF with the Rotofor cell in the pH range of 3-9.5, it has been possible to isolate pure jacalin fractions cont aining fewer number of charged isomers. A single jacalin isoform was i solated by subjecting a Rotofor fraction containing fewer charged spec ies to preparative IEF on thin layer polyacrylamide gel and eluting th e band of interest from the gel. The isolated jacalin isoform was biol ogically active as it agglutinated erythrocytes. The study reveals the complexity of jacalin as it exists as multiple charge isomers over a broad pH range. By performing preparative IEF in solution as well as i n thin layer polyacrylamide gels, it was possible to isolate a single jacalin isoform with the retention of biological activity.