Lectins manganese

To immobilize a protein the biologic activity of which depends on a cofactor, this cofactor has to be present in sufficient concentration during the immobilization step. Thus, for example, the lectin Concanavalin A is immobilized in the presence of a buffer containing 0.1 M glucose or a-methylmannoside, 1 mM calcium chloride and 1 mM manganese chloride. 

For additional references of early work on lectins see Lis and Sharon (ref. 2). t Abbreviations Con A, concanavalin A (which refers to the protein with a full complement of manganese and calcium, i.e., the holoprotein) aMeMan, methyl -D-mannopyranoside aMeGlc, methyl a-D-glucopyranoside /JIphGlc, /J-(O-iodophenyl) D-glucopyranoside 0IphGal,... 

Due to the vast amount of recent research on lectins, it is quite apparent that proteins which bind to specific cell-surface glycoproteins are involved in modulation of a variety of mitotic and metabolic events within the cell. It is hoped that structural studies of these proteins and their receptors will prove to be informative in determining the mechanisms of these and other such events. In this presentation, I would like to discuss the structural features of Con A, such as the /3-sheets, subunit structure, the manganese, calcium and carbohydrate binding sites and close, by mentioning some recent advances in crystallography which are relevant to the studies of proteins and how these should effect such future research. 

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). 

Manganese(II) in Concanavalin A and Other Lectin Proteins A. Joseph Kalb(Gilboa), Jarjis Habash, Nicola S. Hunter,... 

Occasionally the membrane is seen attached to cells in suspension culture (Fig. 5.1.2B). This membrane is associated with a variety of unusual structures containing phenolic residues and tannin. The role of these membranes or skins in osmotic phenomena, filtration, gas exchanges, lectin and enzyme partitioning, and energy transduction at or on surfaces is unknown. Lectins are associated usually with juvenile tissues, such as embryos and seeds, rather than with mature tissues (19, 20). However, lectins that bind manganese and zinc have been isolated from the bark of Robinia pseudoacacia (68). 

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