Lectins with polysaccharides, glycoproteins

Although the interaction of lectins with polysaccharides, glycoproteins, and glycolipids is, without dispute, more complex than with simple sugars, the results of hapten-inhibition studies employing... 

Some typical biological interactions, frequently used in affinity chromatography are enzyme to substrate analogue, inhibitor, or cofactor antibody to antigen, virus, or cell lectin to polysaccharide, glycoprotein, cell surface receptor, or cell nucleic acid to complementary base sequence, histones, or nucleic acid polymerase hormone or vitamin to receptor, or carrier protein glutathione to glutathione-S-transferase (GST) or GST fusion proteins and metal ions to poly (His) fusion proteins, or native proteins with histidine, cysteine and/or tryptophan residues on their surfaces. 

The reaction of partially purified, lima-bean lectin with hog gastric-mucin type A substance exemplified the precipitin-like curve obtained for lectin-polysaccharide or -glycoprotein reactions.103 Classical precipitin-curves between purified components II and III and type A blood-group substance were also obtained.151,199 Maximal precipitation of component II (equivalence) occurred at a lower ratio of A substance per mole of protein than for component III. Under conditions where type A substance precipitated 90% of the lectin, types A2 and B precipitated151,199 66 and 13%, respectively, of component II, and 21 and 0% of component III. Neither of the lima-bean lectins precipitated with type O blood-group substance. 

Information on the existence of viral lectins with specificities other than for sialic acid is scant. Thus, parvovirus B19 binds GalNAc( 31-3)Gal(al-4)Gal( 31-4) [13], Simplex virus binds heparan sulfate [35] and HIV recombinant envelope glycoproteins interact specifically with certain A-linked carbohydrate units of glycoproteins, e.g. of the oligomannose type, with mannose-6-phosphate and sulfated polysaccharides, such as heparin and dextran sulfate [36,37]. 

The content by weight of carbohydrate in glycoproteins may vary from only a few percent to over 50 percent in some proteins in mucous secretions. Although the function of the polysaccharide in most glycoproteins is unknown, in some cases it may provide hydrophilicity, recognition, and points of noncovalent interaction with other proteins through lectin-like affinity binding. 

Insoluble concanavalin A has already been used in the purification of glycoproteins,and, in view of its commercial availability, it will no doubt prove useful in structural, studies. Furthermore, the in-solubilized lectin may be used in column form for the separation of monosaccharide mixtures and of polysaccharide mixtures " it has been demonstrated that mixtures of carbohydrates not separable by complex-formation with concanavalin A in solution may be separated by using the immobilized form,... 

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