PURIFICATION OF 2 LECTINS FROM A NOPALIN AGROBACTERIUM-TUMEFACIENS STRAIN

Lectins were evidenced on the surface of one Agrobacterium tumefaciens wild strain (82.139) by agglutination test and neoglycoprotein labell ing. Bacteria were incubated in the presence of various fluorescein-la belled neoglycoproteins and the binding was assessed by a fluorimetric method. Among the fluorescein-labelled neoglycoproteins tested, the o ne bearing alpha-D-galactosyl residues was the most efficient. The lab elling was optimal at pH 5.0 and naught at pH above 7, The binding was specifically inhibited by homologous fluorescein-free neoglycoprotein s. A galactoside-specific lectin was purified to homogeneity by affini ty chromatography on agarose-A4 substituted with alpha-D-galactopyrano syl residues. Upon polyacrylamide gel electrophoresis, a single band ( M-r 58 000) was detected. This alpha-D-galactoside-specific lectin agg lutinated preferentially human B red blood cells at pH 5.0. Another le ctin specific for alpha-L-rhamnoside (M-r 40 000) not retained on the immobilised galactose was purified by affinity chromatography on alpha -L-rhamnosyl substituted agarose-A4. This L-rhamnoside-specific lectin preferentially agglutinated horse erythrocytes. On the basis of their M-r and on their sugar specificity these two lectins are novel lectin s with regard to the known sugar-binding proteins present in the Rhizo biaceae family: Agrobacterium, Rhizobium or Bradyrhizobium strains. (( C) Societe francaise de biochimie et biologie moleculaire/Elsevier, Pa ris).