Polyvalent GalNAcalpha1-->Ser/Thr (Tn) and Galbeta1-->3GalNAcalpha1-->Ser/Thr (T alpha) as the most potent recognition factors involved in Maclura pomifera agglutinin-glycan interactions.
The agglutinin isolated from the seeds of Maclura pomifera (MPA) recognizes a mucin-type disaccharide sequence, Galbeta1-->3GalNAc (T) on a human erythrocyte membrane. We have utilized the enzyme-linked lectinosorbent assay (ELLSA) and inhibition assay to more systematically analyze the carbohydrate specificity of MPA with glyco-recognition factors and mammalian Gal/GalNAc structural units in lectin-glycoform interactions. From the results, it is concluded that the high densities of polyvalent GalNAcalpha1-->Ser/Thr (Tn) and Galbeta1-->3GalNAcalpha1-->Ser/Thr (T(alpha)) glycotopes in macromolecules are the most critical factors for MPA binding, being on a nanogram basis 2.0 x 10(5), 4.6 x 10(4) and 3.9 x 10(4) more active than monovalent Gal, monomeric T and Tn glycotope, respectively. Other carbohydrate structural units in mammalian glycoconjugates, such as human blood group Sd (a+) related disaccharide (GalNAcbeta1-->4Gal) and Pk/P1 active disaccharide (Galalpha1-->4Gal) were inactive. These results demonstrate that the configurations of carbon-4 and carbon-2 are essential for MPA binding and establish the importance of affinity enhancement by high-density polyvalencies of Tn/T glycotopes in MPA-glycan interactions. The overall binding profile of MPA can be defined in decreasing order as high density of polyvalent Tn/T(alpha) (M.W. > 4.0 x 10(4)) >> Tn-containing glycopeptides (M.W. < 3.0 x 10(3)) > monomeric T/Tn and P (GalNAcbeta1-->3Gal) > GalNAc > Gal >> Man, L: ARA: , D: Fuc and Glc (inactive). Our findings should aid in the selection of this lectin for elucidating functions of carbohydrate chains in life processes and for applications in the biomedical sciences.
Wu
Albert M
AM
Glyco-Immunochemistry Research Laboratory, Institute of Molecular and Cellular Biology, College of Medicine, Chang-Gung University, Kweishan, Taoyuan 333, Taiwan. amwu@mail.cgu.edu.tw
D000818:Animals; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000378:metabolism*; D001789:Blood Group Antigens / Q000737:chemistry / Q000378:metabolism; D002240:Carbohydrate Sequence; D004912:Erythrocytes / Q000737:chemistry / Q000166:cytology; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D037102:Lectins / Q000378:metabolism; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism; D037121:Plant Lectins / Q000378:metabolism*
D015295:Antigens, Tumor-Associated, Carbohydrate; D001789:Blood Group Antigens; D006023:Glycoproteins; D037102:Lectins; D009844:Oligosaccharides; D037121:Plant Lectins; C040286:Tn antigen; C034551:maclurin; C016467:Thomsen-Friedenreich antigen