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Updated: Jul 8, 2026
Exploring Protein-Glycan Interactions: Advances in Nuclear Magnetic Resonance
Published on: August 26, 2025
Structural basis for mannose recognition by a lectin from opportunistic bacteria Burkholderia cenocepacia
Emilie Lameignere1, Lenka Malinovská, Margita Sláviková
1CERMAV-CNRS, BP 53, F-38041, Grenoble, Cedex 09, France.
Abstract:
Chronic colonization of the lungs by opportunist bacteria such as Pseudomonas aeruginosa and members of the Bcc (Burkholderia cepacia complex) is the major cause of morbidity and mortality among CF (cystic fibrosis) patients. PA-IIL (lecB gene), a soluble lectin from Ps. aeruginosa, has been the subject of much interest because of its very strong affinity for fucose. Orthologues have been identified in the opportunist bacteria Ralstonia solanacearum, Chromobacterium violaceum and Burkholderia of Bcc. The genome of the J2315 strain of B. cenocepacia, responsible for epidemia in CF centres, contains three genes that code for proteins with PA-IIL domains. The shortest gene was cloned in Escherichia coli and pure recombinant protein, BclA (B. cenocepacia lectin A), was obtained. The presence of native BclA in B. cenocepacia extracts was checked using a proteomic approach. The specificity of recombinant BclA was characterized using surface plasmon resonance showing a preference for mannosides and supported with glycan array experiments demonstrating a strict specificity for oligomannose-type N-glycan structures. The interaction thermodynamics of BclA with methyl alpha-D-mannoside demonstrates a dissociation constant (K(d)) of 2.75 x 10(-6) M. The X-ray crystal structure of the complex with methyl alpha-D-mannoside was determined at 1.7 A (1 A=0.1 nm) resolution. The lectin forms homodimers with one binding site per monomer, acting co-operatively with the second dimer site. Each monomer contains two Ca2+ ions and one sugar ligand. Despite strong sequence similarity, the differences between BclA and PA-IIL in their specificity, binding site and oligomerization mode indicate that the proteins should have different roles in the bacteria.
Insights
Researchers characterized BclA, a lectin from Burkholderia cenocepacia, finding it binds specifically to mannose-containing glycans. This discovery offers insights into bacterial interactions in cystic fibrosis lung infections.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- Chronic lung infections by Pseudomonas aeruginosa and Burkholderia cepacia complex (Bcc) bacteria are major causes of mortality in cystic fibrosis (CF) patients.
- Bacterial lectins, like PA-IIL from Ps. aeruginosa, play roles in host-pathogen interactions by binding to host glycans.
- PA-IIL exhibits strong affinity for fucose, and similar lectins are found in other opportunistic pathogens.
Purpose of the Study:
- To characterize a novel lectin, BclA (Burkholderia cenocepacia lectin A), from the CF pathogen B. cenocepacia.
- To determine the binding specificity and structural properties of BclA.
- To compare BclA with other known bacterial lectins like PA-IIL to understand potential functional differences.
Main Methods:
- Cloning and expression of the shortest PA-IIL-like gene from B. cenocepacia J2315 in Escherichia coli to obtain recombinant BclA.
- Proteomic analysis to confirm the presence of native BclA in B. cenocepacia extracts.
- Surface plasmon resonance and glycan array experiments to characterize BclA's binding specificity.
- Isothermal titration calorimetry to determine binding thermodynamics.
- X-ray crystallography to elucidate the complex structure of BclA with a mannoside ligand.
Main Results:
- Recombinant BclA was successfully produced and confirmed in bacterial extracts.
- BclA demonstrated strict specificity for oligomannose-type N-glycans, preferring mannosides over fucose.
- Thermodynamic analysis revealed a dissociation constant (Kd) of 2.75 x 10^-6 M for methyl alpha-D-mannoside.
- X-ray crystallography at 1.7 Å resolution showed BclA forms homodimers with cooperative binding sites, each monomer binding two Ca2+ ions and a sugar ligand.
- Structural and specificity differences were noted between BclA and PA-IIL, suggesting distinct biological roles.
Conclusions:
- BclA is a distinct lectin from B. cenocepacia with specific binding to mannose-containing glycans.
- The structural and functional differences between BclA and PA-IIL suggest they mediate different roles in bacterial pathogenesis or interaction.
- Further research into BclA's function could reveal new therapeutic targets for CF lung infections.
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