| Description |
Plant and animal pathogens use protein-carbohydrate interactions in their strategy for host recognition and invasion. The comprehension of the molecular mechanisms, which gives a pathogenic bacterium the ability to invade, colonize and reorient the physiopathology of its host, is a goal of primary importance and such studies may direct the conception of new strategies to fight against these pathogenic agents. Ralstonia solanacearum is a plant bacterial pathogen. It causes a wilt disease in several economically important agricultural crops, such as potatoes, tomatoes, peppers, eggplant and banana [1]. Cases of this disease are known as Southern wilt, bacterial wilt, and brown rot of potato. The disease is transmitted through soil, contaminated water, equipment, personnel, and by transplanting infected plants. It is not spread through the air, from plant to plant through the splashing of water. Lectins are sugar-binding proteins of non-immune nature that agglutinate cells or precipitate glycoconjugates. They recognize sugar moieties in cell walls or membranes and thereby change the physiology of the membrane to cause agglutination, mitosis, or other biochemical changes in the cell. Their specificity is usually defined by the monosaccharides or oligosaccharides that are the best at inhibiting the agglutination or precipitation induced by the lectin. Lectins are of interest because of their wide variety of properties and potential applications (pharmacology, immunology, cancer therapy, agriculture, etc.). As far as we know, the R. solanacearum bacterium has been producing three soluble lectins. RSL (MW 9900), which exhibits sugar specifity to L-fucose [2] and partial sequence homology to mushroom Aleuria aurantia lectin AAL [3], RS-IIL (MW 11601) lectin [4] resembles PA-IIL, from human pathogen Pseudomonas aeruginosa in structure and properties but differs in sugar specifity [5]. The last one is RS20L (MW 19903), which is described in the present study. This contribution structurally and functionally describes RS20L, which has no sequence similarity to any known amino acid sequence. Although resolution of crystal structure showed high structural similarity to animal galectins, it does not display sugar specifity to D-galactose. Further functional studies using gel permeation chromatography (GPC), surface plasmon resonance (SPR), isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) allowed to define binding properties and thermodynamic parameters.
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