Unusual Entropy-Driven Affinity of Chromobacterium violaceum Lectin CV-IIL Towards Fucose and Mannose
| Authors | |
|---|---|
| Year of publication | 2006 |
| Type | Article in Periodical |
| Magazine / Source | Biochemistry |
| MU Faculty or unit | |
| Citation | |
| Field | Biochemistry |
| Keywords | Chromobacterium violaceum;monosaccharide;lectin;affinity |
| Description | The purple pigmented bacterium Chromobacterium violaceum is a dominant component of tropical soil micorbiota that cause rare but fatal septicaemia in humnas. Its sequenced genome provides insight into the abundant potential of this organism for biotechnological and pharmaceutical app;ications and allowed an ORF encoding a protein that is 60% identical to tha fucese bindient lectin (PA-IIL) from Pseudomonas aeruginosa and the mannose binding lectin (RS-IIL) from Ralstonia solanacearum to be identified. The lectin, CV-IIL, has recently been purified from C. violaceum [1] and has been confirmed to be a tetramer with subunit size of 11.86 kDa and a binding preference for fucose. We describe here tha cloning of CV-IIL and its expression as a recombinant protein. A complete structure-function characterization has been made in an effort to analyze tha specificity and affinity of CV-IIL for fucose and mannose. Crystal structures of CV-IIL complexes with monosaccharides have yielded the molecular basis of the specificity. Each monomer contains two close calcium cations that mediate the binding of the monosaccharides, which occures in different orientations for fucose and mannose. The thermodynamics of binding has been analyzed by titration microcalorimetry, giving dissociation constants of 1.7 and 19 uM for a-methyl fucoside and a-methyl mannoside, respectively. Further analysis demonstrated a strongly favorable entropy term that is unusual in carbohydrate binding. A comparison with both PA-IIL and RS-IIL, which have binding preferences for fucose and mannose, respectively, yieldes insights into the monosaccharide specificity of this important class of soluble bacterial lectins. |
| Related projects: |