The fucose-binding lectin from Ralstonia solanacearum: a new type of beta-propeller architecture formed by oligomerisation and interacting with fucoside, fucosyllactose and plant xyloglucan
| Title in English | The fucose-binding lectin from ralstonia solanacearum: a new type of beta-propeller architecture formed by oligomerisation and interacting with fucoside, fucosyllactose and plant xyloglucan |
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| Authors | |
| Year of publication | 2005 |
| Type | Article in Periodical |
| Magazine / Source | Journal of Biological Chemistry |
| MU Faculty or unit | |
| Citation | |
| Field | Biochemistry |
| Keywords | lectin; Ralstonia solanacearum; crystal structure; propeller; SPR |
| Description | Plant pathogens, as animal ones, use protein-carbohydrate interactions in their strategy for host recognition, attachment and invasion. The bacterium Ralstonia solanacearum which is distributed worldwide and causes lethal wilt in many agricultural crops, was shown to produce a potent L-fucose-binding lectin, RSL, a small protein of 90 amino acids with a tandem repeat in its amino acid sequence. In the present study, surface plasmon resonance experiments conducted on a series of oligosaccharides show a preference for binding to áFuc1-2Gal and áFuc1-6Gal epitopes. Titration microcalorimetry demonstrates the presence of two binding sites per monomer and an unusually high affinity of the lectin for áFuc1-2Gal containing oligosaccharides (KD 2.5 10-7 M for 2-fucosyllactose). RSL has been crystallised with a methyl derivative of fucose and with the highest affinity ligand, 2-fucosyllactose. X-ray crystal structures, the one with á-methyl-fucoside being at ultra-high resolution, reveal that each monomer consists of two small fourstranded anti-parallel â-sheets. Trimerisation through 3-fold or pseudo 3- fold axis generates a six-bladed â-propeller architecture, very similar to that previously described for the fungal lectin of Aleuria aurantia. This is the first report of a â- propeller formed by oligomerisation and not by sequential domains. Each monomer presents two fucose binding sites, resulting in six symmetrically arranged sugar binding sites for the â-propeller. Crystals were also obtained for a mutated lectin complexed with a fragment of xyloglucan, a fucosylated polysaccharides from the primary cell wall of plants, which may be the biological target of the lectin. |
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