Characterization and molecular cloning of the lectin from 
Helianthus tuberosus

Abstract

A lectin called Helianthus tuberosus agglutinin or Heltuba has been isolated from tubers of the Jerusalem artichoke, a typical representative of the Asteraceae family. Heltuba is a tetrameric protein composed of four identical subunits of 15.5 kDa and exhibits a preferential specificity towards oligomannosides. Cloning of the corresponding cDNAs revealed that the mature lectin polypeptide comprises the entire open reading frame of the cDNA suggesting that the primary translation product is not processed and that the lectin is a cytosolic protein. Searches in the databases revealed sequence similarity with lectins from the taxonomically unrelated Convolvulaceae and Moraceae species. Therefore, the discovery of Heltuba is of great importance in view of the occurrence and molecular evolution of the jacalin-related lectins.

Structural basis for the unusual carbohydrate-binding specificity of jacalin towards galactose and mannose

“…The overall shape of the cleft forming the carbohydratebinding site is far more extended in jacalin than in the mannosebinding jacalin-related lectins, which exhibit a more restricted specificity for mannose and glucose (Figure 4) [33,34]. As a result, the binding site of jacalin can accommodate epimeric sugars with differently oriented C-2 and C-4 hydroxyl groups and more or less bulky substituents.…”

Characterization, Occurrence, and Molecular Cloning of a Lectin fromGrifola frondosa: Jacalin-Related Lectin of Fungal Origin

“…7). A lectin (Heltuba) from the tuber of Jerusalem artichoke (Helianthus tuberosus) 12) showed 26.1% identity over 111 amino acids (nos. 57-167 of GFL/nos.…”

“…The amino acid sequence of GFL showed about 25% homology with those of two plant lectins. 12,13) These lectins are members of the so-called jacalin-related lectins, suggesting that GFL is also a jacalin-related lectin of fungal origin.…”

The Expression Profile of Lectin Differs from That of Seed Storage Proteins inCastanea crenataTrees

“…To date, the former has been isolated only in the Moraceae, [6][7][8] while the latter has been widely observed throughout the plant kingdom in, for example, dicots, [8][9][10][11] monocots, 12,13) gymnosperms, 14) and true ferns. 15) Because these lectins recognize foreign glycans and because some are induced by jasmonate, 12) they are assumed to be defense proteins.…”