STRUCTURE – FUNCTION STUDIES OF RS20L LECTIN FROM THE BACTERIUM Ralstonia solanacearum

Nikola Kostlánová¹, Edward Mitchell², Ondřej Šulák¹, Nechama Gilboa-Garber³, Anne Imberty⁴ a Michaela Wimmerová^1,5

¹National Centre for Biomolecular Research & ⁵Department of Biochemistry Masaryk University, Brno, Czech Republic

²E.S.R.F Experiment Division, BP220, F-38043 Grenoble cedex,France,

³CERMAV-CNRS, BP 53, F-38041 Grenoble cedex 09, France,

⁴Bar-Ilan University, Faculty of Life Science, Ramat Gan 52900, Israel

Lectins are sugar-binding proteins of non-immunoglobulin nature that agglutinates cells or precipitates glycoconjugates. Their specificity is usually defined by the monosaccharides or oligosaccharides that are best at inhibiting the agglutination or precipitation the lectin causes. Lectins are of interest because of their wide variety of properties and potential applications (pharmacology, immunology, cancer therapy, agriculture...).

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 bacterial pathogen, which causes a wilt disease in several economically important agricultural crops, such as potatoes, tomatoes, peppers, eggplant, banana... [0] Causes 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. The bacterium R. solancearum is a widely accepted model organism for the study of pathogenicity in plants.

Until our knowledge now, the R. solanacearum bacterium has been producing three soluble lectins. RSL (MW 9900), which exhibits sugar specifity to L-fucose [0] and partial sequence homology to mushroom Aleuria aurantia lectin AAL [0], RS-IIL (MW 11601) lectin [0] resembles PA-IIL from human pathogen Pseudomonas aeruginosa in structure and properties but differs in sugar specifity [0]. The last one is RS20L (MW 20034), which displays mannose and xylose binding ability.

This short communication structurally and functionally describes RS20L, a 20kDa lectin from R. solanacearum, which has no sequence similarity to any known lectin amino acid sequence, but resolution of crystal structure showed high structural similarity to animal galectins.

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