Concanavalin tetrameric form

Concanavalin A.—The interactions of metal ions with the transition-metal SI, and calcium-ion, S2, binding sites of concanavalin A have attracted some attention. Each protomer of molecular weight 27 000 has one SI and one S2 site and the protein exists in a dimeric form, pH < 5.5, and tetrameric form, pH > 7.0. Metal ion binding has been studied using the fluorescence quenching of 4-methyl-umbelliferyl-a-D-mannopyranoside (MUM), a sugar residue which binds to the protein in its various metallated forms ... 

Four different dimeric and three different tetrameric structures have been described to date. In the most common dimer the back sheets of the lectin monomers associate to form a continuous 12-stranded p-sheet along the length of the dimer (Figure 2A). This dimer, called the canonical legume lectin dimer has been found in most legume lectins studied [26]. In some lectins these dimers combine to form tetramers of which there are two types. In the case of concanavalin A, the dimers interface at the central parts of their back sheets to form a structure as shown in Figure 2B. In the case of such lectins as PHA-L, the soybean agglutinin and the D. biflorus seed lectin, the dimers interface at the outermost strands of the 12-stranded P-sheets to... 

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