Carbohydrate specificity of a toxic lectin, abrin A, from the seeds of Abrus precatorius (jequirity bean).
To elucidate of the mechanism of intoxication, the affinity of a toxic lectin, abrin A, from the seeds of Abrus precatorius for mammalian carbohydrate ligands, was studied by enzyme linked lectinosorbent assay and by inhibition of abrin A-glycan interaction. From the results, it is concluded that: (1) abrin A reacted well with Gal beta1-->4GlcNAc (II), Gal alpha1-->4Gal (E), and Gal beta1-->3GalNAc (T) containing glycoproteins. But it reacted weakly with sialylated gps and human blood group A,B,H active glycoproteins (gps); (2) the combining site of abrin A lectin should be of a shallow groove type as this lectin is able to recognize from monosaccharides with specific configuration at C-3, C-4, and deoxy C-6 of the (D)Fuc pyranose ring to penta-saccharides and probably internal Gal alpha,beta-->; and (3) its binding affinity toward mammalian structural features can be ranked in decreasing order as follows: cluster forms of II, T, B/E (Gal alpha1-->3/4Gal) > monomeric T > monomeric II > monomeric B/E, Gal > GalNAc > monomeric I >> Man and Glc (inactive). These active glycotopes can be used to explain the possible structural requirements for abrin A toxin attachment.
Wu
A M
AM
Glyco-Immunochemistry Research Laboratory, Institute of Molecular & Cellular Biology, College of Medicine, Chang-Gung University, Kwei-San, Tao-Yuan, Taiwan. amwu@mail.cgu.edu.tw
Wu
J H
JH
Herp
A
A
Chow
L P
LP
Lin
J Y
JY
D000036:Abrin / Q000378:metabolism*; D002240:Carbohydrate Sequence; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D007124:Immunoenzyme Techniques; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*; D037121:Plant Lectins; D011485:Protein Binding; D019685:Rosales / Q000196:embryology*; D012639:Seeds / Q000378:metabolism*
D006023:Glycoproteins; D009844:Oligosaccharides; D037121:Plant Lectins; D000036:Abrin