Lectins galactose-specific

D. K. Mandal and C. F. Brewer, Crosslinking activity of the 14-kilodalton -galactose-specific vertebrate lectin with asialofetuin Comparison with several galactose-specific plant lectins, Biochemistry, 31 (1992) 8465-8472. 

Many lectins combine preferentially with a single sugar structure, for example g-galactose or L-fucose. For some lectins the specificity is broader and includes several closely related sugars, e.g., D-man-nose, g-glucose and g-arabinose other lectins-interact only with complex carbohydrate structures such as those that occur in glycoproteins, glycolipids,... 

Tighter binding is observed if additional mannose residues are present in an oligosaccharide.The protein also has specific binding sites for Ca + and for a transition metal ion such as Mn +. Soybean lectin binds D-N-acetylgalactosamine and o-galactose units, while wheat lectin is specific for o-N-acetylglucosamine. 

RT is the major protein of the Ricinus communis seed. It is composed of two polypeptide chains, RTA and RTB, of approx the same molecular mass (30-32 kDa) linked to each other with a disulfide bond (Fig. 2). RTA is an N glycosidase, which removes a specific adenine residue from the 28S ribosomal RNA, thereby inhibiting protein synthesis. The RTB chain is a galactose-specific lectin that allows the RT to bind to the cell-surface glycoproteins and glycolipids on virtually all mammalian cells. Both chains also contain carbohydrate moieties, which are responsible, at least in part, for their interaction with the carbobydrate-binding lectins of liver cells. The procedure used in our laboratory for isolation and purification of RT and its RTA chain is as follows (Fig. 6). 

Among the fungal and protozoal lectins only a few have been studied in detail. One of these is the galactose-specific lectin of the protozoa Entamoeba histolytica. It mediates adhesion of the parasite to human colonic mucin glycoproteins and has a central role in the contact-dependent cytolysis or histolysis for which the parasite is named. A sialic-acid-speeific lectin has been isolated from merozoites of the human malarial parasite, Plasmodium falciparum. An unusual lectin is that of the protozoan Giardia lamblia, specific for mannose-6-phosphate, which is activated by trypsinization. 

In effect, several lectins including galactose-specific lectin [94] and DEC-205 receptor [95] on cell surfaces could potentially bind the saponin sugar residues to assure targeting. This same delivery mechanism would assure that the same APC receiving the antigen would receive a stimulatory signal from the adjuvant. 

For instance, maleic copolymers with different contents of galactose moieties and dodecyl chains were synthesized and used as both a stabilizer and a surface coating for the preparation of poly(s-caprolactone) nanoparticles by the emulsification-diffusion technique. The smface modification of nanoparticles was confirmed by -potential measurements. Nanoparticles were also shown to be recognized by a galactose-specific lectin, demonstrating the presence of galactose rmits on the particle surface [69],... 

The glycosylation can further be demonstrated by affinity chromatography on a galactose-specific immobilized lectin. The test was done on a PNA-Sepharose column with native and modified chymotrypsins. The chymotrypsin-galactose peak was shifted compared to the native enzyme. All the enzyme molecules were modified it was possible to follow the modification of the physico-chemical properties of the derivatized enzyme without further purification. 

An AB block copolymer of polyCy-benzyl L-glutamate) and poly(ethylene oxide) has been made with a lactonamide group at the terminus. This polymer caused adhesion of rat hepatoc rtes which have galactose-specific lectins on their cell surfaces.22... 

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