Concanavalin saccharide-binding site

Derewenda Z, Yariv J, Helliwell JR, Kalb AJ, Dodson EJ, Papiz MZ, Wan T, Campbell J. The structure of the saccharide-binding site of concanavalin A. EMBO J 1989 8 2189-2193. 

An interesting point is that manganese, as well as other divalent transition metals, plays an essential role in saccharide binding in concanavalin A, a member of the plant proteins which are also known as hemagglutinins or plant lectins. Concanavalin A occurs in quantities of > 5% DM in legumes (e.g., the Jack bean, Canavalia ensi-formis). The function of plant lectins in saccharide binding sites is unknown, but a defense mechanism may be involved (Kalb (Gilboa) et al. 2000). 

A study of the interaction of a number of immunoglobulin-derived gjyco-peptides with concanavalin A has shown that the binding depends on terminal 2-acetamido-2-deoxy-j8-D-glucosyl and a-o-mannosyl residues and on internal D-mannosyl residues substituted at C-2. The saccharide-binding site seems to be capable of binding several sugar residues. The inhibition indexes of several... 

The lectins are saccharide-binding proteins that cause cell agglutination. The best characterized of the lectins is concanavalin A (Con A). Con A is devoid of carbohydrate binding activity in the absence of added metal. Each monomeric unit of Con A has two binding sites, named SI (the transition metal site) and S2 (the calcium site). The SI site binds a variety of divalent transition metals, including Mn, Ni, Co, Cd, Zn, Fe, and Cu, although Mn is probably the metal used in vivo. The S2 site is not formed until SI is occupied. Both SI and S2 must be occupied before saccharide will bind. 

Aggregation of concanavalin A by low concentrations of sodium dodecyl sulphate requires the presence of an intact saccharide-ligand binding site. A rapid... 

Identical rate constants have been reported for saccharide binding to concanavalin A when Mn +, Co " ", or Zn + occupy the S-1 site and Ca + occupies the S-2 site. The affinity of the protein for saccharides is dependent upon the occupancies of both sites and is sensitive to the identity of the metal ions in S-2. 

Identical rate constants have been reported for saccharide-binding by concanavalin A when Mn +, Co +, or Zn + occupy the SI site and Ca + occupies the S2 site. The affinity of the protein for saccharides is dependent upon the metal occupancies of both sites and is sensitive to the identity of the metal ion in site S2. Titrations of metal employing e.s.r. spectroscopy and equilibrium dialysis have revealed that the binding of Mn + to concanavalin A is cooperative in the presence of Ca + and non-co-operative in its absence. The degree of co-operativity also increases with increasing pH. At pH 7.2 only Ca + and not a transition-metal ion is required for saccharide binding to concanavalin A, whereas at pH 5, at which most other studies have been carried out, both a transition metal and Ca + are necessary for binding. ... 

Poly-amido-saccharides (PAS) (Figure 2.9) are synthetic carbohydrates that can mimic natural polysaccharides as they can bind lectin concanavalin A (ConA) at the same site as natural carbohydrates. PAS are synthesised via anionic ROP of a P-lactam sugar monomer. In PAS, the pyranose rings are linked through the 1- and 2-positions by an amide with a-stereochemistry. P-lactam sugar is synthesised from benzyl-protected D-glucal [56]. 

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