Conserved Site

Legume lectin, alpha chain, conserved site (IPR000985)

Short name: Lectin_LegA_CS

Description

Legume lectins are one of the largest lectin families with more than 70 lectins reported [PMID: 2227211, PMID: 3527046]. Leguminous plant lectins resemble each other in their physicochemical properties although they differ in their carbohydrate specificities. They consist of two or four subunits with relative molecular mass of 30 kDa and each subunit has one carbohydrate-binding site. The interaction with sugars requires tightly bound calcium and manganese ions. The structural similarities of these lectins are reported by the primary structural analyses and X-ray crystallographic studies. X-ray studies have shown that the folding of the polypeptide chains in the region of the carbohydrate-binding sites is also similar, despite differences in the primary sequences. The carbohydrate-binding sites of these lectins consist of two conserved amino acids on beta pleated sheets. One of these loops contains transition metals, calcium and manganese, which keep the amino acid residues of the sugar-binding site at the required positions. Amino acid sequences of this loop play an important role in the carbohydrate-binding specificities of these lectins. These lectins bind either glucose/mannose or galactose.

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.

Some legume lectins are proteolytically processed to produce two chains, beta (which corresponds to the N-terminal) (IPR001220) and alpha (C-terminal). The lectin concanavalin A (conA) from Canavalia ensiformis (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.

The signature pattern of the entry is located in N-terminal of the alpha chain.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns