PURIFICATION OF AN ALPHA-L-FUCOSIDE-BINDING PROTEIN FROM RHIZOBIUM-LUPINI

Lectins associated with the bacterial cell surface of Rhizobium lupini strain LL13 were evidenced by erythrocyte agglutination, by aggregati on of neoglycoprotein coated beads and by spectrofluorimetry using flu oresceinylated neoglycoproteins. At pH 5.0, a specific binding of the fluorescein-labelled neoglycoprotein bearing alpha-L-fucose was observ ed. The binding of this labelled neoglycoprotein is a saturable phenom enon and is inhibited by the same unlabelled neoglycoprotein. Extracts of R lupini obtained by disrupting a bacterial pellet through a Frenc h press were stabilized at pH 5.6 by gel filtration and purified to ho mogeneity by affinity chromatography on Agarose A4 substituted with al pha-L-fucose. A protein with a M(r) approximate to 19 000 was specific ally eluted from this affinity column with L-fucose. Isoelectric focus ing of this sample yielded a single band with pi near 6.7. This protei n specifically aggregated L-Fuc-BSA-coated microspheres. The results o btained in the present study indicate that we have purified from Rhizo bium lupini strain LL13, a L-fucose binding protein as a lectin.