Studies on lectins. LII. Isolation and characterization of the lectin from rye germ (Secale cereale L.).

Abstract

Rye germ lectin was isolated by extraction of defatted rye germ, fractionation of the extract by ammonium sulfate precipitation, affinity chromatography of the active substances on chitin-beta-glucan and gel filtration on Sephadex G-50. The lectin shows erythroagglutinating activity at a minimum concentration of 2.5 micrograms/ml. The erythroagglutinating activity is the same against human red blood cells of all types of the ABO system and is inhibited by N-acetyl-D-glucosamine. The lectin has no mitogenic activity against mouse splenic lymphocytes. According to the results of polyacrylamide gel electrophoresis the lectin obtained is a mixture of three very similar isolectins of equal erythroagglutinating activity. Sedimentation analysis indicates homogeneity of the lectin preparation; the molecular weight was 56000 as estimated by sedimentation equilibrium. In the presence of urea and sodium dodecyl sulfate the lectin dissociates into 2 types of subunits with molecular weights of 35000 and 19000. The rye germ lectin contains about 2% of neutral sugar and 1% of D-glucosamine. The amino acid composition of the lectin is characterized by a very high content of glycine and half cystine and a low content of apolar amino acids. N-terminal amino acids of the lectin are apparently blocked.