Lectins quaternary structures

Phytohaemagglutinins.—pH-Acetyl]concanavalin A has been shown to bind to, and partially inhibit the enzymic activity of, proline 2-oxoglutaratedioxygenase. The products obtained when concanavalin A is labelled with 4-azidophenyl a-D-mannopyranoside under u.v.-irradiation have been separated by affinity chromatography on Sephadex G-lOO at pH 5. One of the products is a monovalent dimer at pH 5 and a divalent tetramer at pH 7, indicating that photo-affinity labelling did not alter the quaternary structure of concanavalin A, although the haemagglutinating activity of the derivatized lectin was reduced. 

Although the monomeric units of different legume lectins are extremely similar with one another, marked variations have been found in their quaternary structures. 

In addition to the above quaternary structures, two additional types of legume lectin dimers have been found in the GS-IV and ECorL lectins, which are both dimeric proteins [26]. The peanut lectin, which is a tetramer, has a unique structure composed of two GS-IV type dimers [27]. Such variation in quaternary structure of the legume lectins may be of significance to the role(s) of these lectins in the plant. 

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