Isolation and Characterization of Amaranthin, a Lectin Present in the Seeds of Amaranthus caudatus, That Recognizes the T- (or Cryptic T)-Antigen (original) (raw)

1989, Journal of Biological Chemistry

Amaranthus caudatus is an ancient plant native to the Andean countries of South America where it was once used as an important food source (1). Although today the Amaranth plant is used principally for ornamental purposes in the United States and Europe, a renewed interest in several Amaranthus species has been expressed due to their nutritional value (1,2). In 1970, Pardoe and co-workers (3) reported that aqueous extracts of A. caudatus seeds contained a lectin which agglutinated A, B, and 0 red blood cells equally well. However, these investigators did not isolate or define the sugar-binding specificity of the lectin. Recently, the isolation of lectins from two Amaranthus species has been described. Zenteno and Ochoa (4) purified a lectin from A. leucocarpus by chromatography on a blood group A stroma column. These investigators reported the lectin to have subunit MI = 45,000, and to be inhibited best by N-acetylgalactosamine and fetuin; the A. leucocarpus lectin was also found to be mitogenic to mouse spleen lymphocytes. In contrast, Pardoe et al. (3) reported that a crude extract of A. caudatus seeds was non-mitogenic to hog lymphocytes. Koeppe and Rupnow (5) described the purification of a lectin from the seeds of A. cruentus using affinity chromatography on fetuin-agarose. The A. cruentus lectin had a subunit M, = 35,000 and a native M, = 66,000, suggesting that this lectin occurs as a homodimer; it was also found to be best inhibited by N-acetylgalactosamine and fetuin. Polyclonal antibodies against the purified A. cruentus lectin gave a reaction of identity with crude seed extracts from various Amaranthus species, including A. caudatus. The Thomsen-Friedenreich antigen (T-antigen)' has been ' The abbreviations used are: T-antigen, GalB1,3GalNAccr-O-; GalNAc, 2-acetamido-2-deoxy-~-galactose; GalN, 2-amino-2-deoxy-D-galactose; Fuc, fucose; AOSM, asialo-ovine submaxillary mucin; AFGP, antifreeze glycoprotein (M , = 10,500); AFGP-8, antifreeze glycoprotein (M, = 2,600); PBS, phosphate-buffered saline, pH 7.2; BSA, bovine serum albumin; PNA, peanut (Arachis hypogaea) agglutinin; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; Synsorb-T, beads derivatized with the disaccharide Ga1~1,3GalNA~or-O-(CH~)~C0.