InterPro domain: IPR016363

This group represents L-type lectins from plants, including leukoagglutinins which bind sialic acid [ 1 ].

Lectins are carbohydrate-binding proteins. Leguminous lectins form one of the largest lectin families and resemble each other in their physicochemical properties, though they differ in their carbohydrate specificities. They bind either glucose/mannose or galactose [ 2 ]. Carbohydrate-binding activity depends on the simultaneous presence of both acalcium and a transition metal ion [ 3 ]. The exact function of legume lectins is not known, but they may be involved in the attachment of nitrogen-fixing bacteria to legumes and in the protection against pathogens [ 4 , 5 ].

Some legume lectins are proteolytically processed to produce two chains, beta (which corresponds to the N-terminal) and alpha (C-terminal) [ 6 ]. The lectin concanavalin A (conA) from jack bean is exceptional in that the two chains are transposed and ligated (by formation of a new peptide bond). The N terminus of mature conA thus corresponds to that of the alpha chain and the C terminus to the beta chain [ 7 ]. Though the legume lectins monomer is structurally well conserved, their quaternary structures vary widely [ 8 ].

1. The immobilized leukoagglutinin from the seeds of Maackia amurensis binds with high affinity to complex-type Asn-linked oligosaccharides containing terminal sialic acid-linked alpha-2,3 to penultimate galactose residues. J. Biol. Chem. 263, 4576-85
2. Legume lectins--a large family of homologous proteins. FASEB J. 4, 3198-208
3. Legume lectin structure. Biochim. Biophys. Acta 1383, 9-36
4. Dual-function protein in plant defence: seed lectin from Dolichos biflorus (horse gram) exhibits lipoxygenase activity. Biochem. J. 395, 629-39
5. The Rhizobium--legume symbiosis. Proc. R. Soc. Lond., B, Biol. Sci. 204, 219-33
6. Bowringia mildbraedii agglutinin: polypeptide composition, primary structure and homologies with other legume lectins. Biochim. Biophys. Acta 1202, 38-46
7. Polypeptide ligation occurs during post-translational modification of concanavalin A. Nature 313, 64-7