Isolation and partial characterisation of galactose-specific lectins from African yam beans, Sphenostyles stenocarpa Harms

A new galactose-specific lectin was isolated from African yam bean (Sphenos tyles stenocarpa Harms) by affinity chromatography on galactose-Sepharose 4 B. SDS-PAGE analysis resulted in four polypeptide bands of approximately 27 , 29, 32 and 34 kDa, respectively. Based on the analysis of carbohydrate co ntent and native PAGE, it is likely that the Sphenostyles lectin is a tetra meric glycoprotein with M-r of approximately 122 kDa. N-terminal protein se quencing of purified lectins from four different Sphenostyles accessions sh ows that the four polypeptides have largely identical amino acid sequences. The sequences contain the conserved consensus sequence F-F-LILG characteri stic of legume lectins, as well as Phaseolus vulgaris proteins in the arcel in-alpha-amylase inhibitor gene family. The lectin agglutinates both rabbit and human erythrocytes, bur with a preference for blood types A and O. Usi ng Western blotting, the lectin was shown to accumulate rapidly during seed development, but levels dropped slightly as seeds attained maturity. This is the first time a lectin has been purified from the genus Sphenostyles. T he new lectin was assigned the abbreviation LECp.SphSte.se.Hga1. (C) 1999 E lsevier Science Ltd. All rights reserved.