Studies on carbohydrate binding to a lectin purified from Streptomyces sp.
The anti-B specific lectin produced by Streptomyces sp. was shown to have two carbohydrate-binding sites with binding constants of 8.3 . 10(3) M-1 (15 degrees C) and 2.2 . 10(3) M-1 (4 degrees C) for L-rhamnose and D-galactose, respectively, calculated according to Scatchard plots. The binding of specific sugars to the lectin not only induced a peculiar ultraviolet difference spectrum showing a blue shift of tryptophan absorption, but also caused crystallization of the lectin at a concentration of 1 mg per ml or more. The solvent-perturbation studies on the lectin showed that the number of solvent-exposed tryptophan (or average extent of exposure) was two in the absence of L-rhamnose, and three in the presence of the sugar. This suggests that one tryptophan residue appears outside as the result of sugar-binding to the lectin, which is reflected by the difference spectra. Oxidation of two tryptophan residues with N-bromosuccinimide led to complete loss of carbohydrate-binding activity of the lectin, indicating that these residues are important for retaining the activity.
D000017:ABO Blood-Group System; D001665:Binding Sites; D001974:Bromosuccinimide; D050260:Carbohydrate Metabolism; D003460:Crystallization; D004121:Dimethyl Sulfoxide; D005690:Galactose / Q000378:metabolism; D006388:Hemagglutinins; D037102:Lectins / Q000302:isolation & purification; D010084:Oxidation-Reduction; D012210:Rhamnose / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013302:Streptomyces / Q000032:analysis*; D014364:Tryptophan
D000017:ABO Blood-Group System; D006388:Hemagglutinins; D037102:Lectins; D014364:Tryptophan; D001974:Bromosuccinimide; D012210:Rhamnose; D005690:Galactose; D004121:Dimethyl Sulfoxide