Novel Recognition by Banana (Musa acuminata) Lectin of Internal α-1,3 and β-1,6-linked D-Glucosyl Residues

Abstract

A new α-Man/Glc binding lectin, designated BanLec, was isolated from banana (Musa acuminata) fruits by Koshte et.al (1990). The extensive study by Peumans et al (2000) indicated that the lectin is present in the pulp of ripe fruits, and related to that from plantain (Musa spp). Goldstein and coworkers (2001) found unexpectedly that this lectin binds not only branched α-mannan and glucan but also linear α-glucans, such as nigeran and elsinan by recognizing their internal 1,3-glucosidic linkages. It also appeared that BanLec binds to some 0-6-branched β-glucans. In the present study the lectin was newly isolated by affinity column of α-1,3-glucan or branched Auricularia β-glucan.; the lectin was dimer of 14 kDa protein. The binding capability of BanLec was confirmed by use of the lectin- conjugated affinity column. Among various linear α-glucans, nigeran (1,3/1,6) and elsinan (1,3/1,4), but pullulan (1,6/1,4) was not able to bind. Interestingly BanLec was found to recognize Agaricus β-1,6-glucan, and other β-1,6-glu- cans, e.g., pustulan and Gyrophora glucan, but not β-1,3-glucans, such as curdlan. Thus, the banana lectin was proved to be a unique lectin, recognizing the specific internal linkages of α- and β-glucans.