PA-IIL like lectins: a common feature of high adaptability of some opportunistic bacteria
| Authors | |
|---|---|
| Year of publication | 2004 |
| Type | Article in Proceedings |
| Conference | Chemica 43S |
| MU Faculty or unit | |
| Citation | |
| Field | Biochemistry |
| Keywords | lectin; pathogen; saccharide |
| Description | Enormous potential of sugar structures gives them a crucial importance in recognition and signalling events. Carbohydrate-mediated recognition plays an important role in the ability of parasitic organisms to adhere to the surface of the host cell in the first step of their invasion and infectivity. For example, Pseudomonas aeruginosa galactose- and fucose-binding lectins (PA-IL and PA-IIL) contribute to the virulence of this pathogenic bacterium, which is a major cause of morbidity and mortality in cystic fibrosis patients [1,2]. Moreover, the PA-IIL lectin displays an affinity for fucose in micromolar range, unusually high for monosaccharide binding. This characteristics is correlated to the remarkable presence of two calcium ions in the binding site of the protein [3]. Database searching in newly sequenced bacterial genomes revealed the presence of PA-IIL like proteins within a limited number of other opportunistic pathogens. All of them are soil inhabitants, are phylogenetically related and in past were usually considered as Pseudomonas spp. At the present time, PA-IIL like gene have been identified in the genomes of phytopathogen Ralstonia solanacearum and of human opportunistic pathogens Chromobacterium violaceum and Burholderia cenocepacia. The latter was found to cause life threatening pulmonary infections in cystic fibrosis patients at a mortality rate of 80% [4]. PA-IIL like proteins from R. Solanacearum (RS-IIL) and C. Violaceum (CV-IIL) have been fully characterized. RS-IIL has been purified from bacteria by affinity chromatography [4] whereas CV-IIL has been obtained in the recombinant form. The three lectins have been compared for their specificity (enzyme amplification method), their affinity for monosaccharides (isothermal titration microcalorimetry experiments) and their crystal structures. Comparison of the structures of the PA-IIL/fucose and RS-IIL/mannose complexes allow us to rationalize the basis of the unusual high specificity of both proteins for monosaccharides and the importance of three amino acid motif for fine tuning of the lectin specificity. |
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