Microbial F-type lectin domains with affinity for blood group antigens

Cellulophaga algicola alginate lyase inhibits biofilm formation of a clinical Pseudomonas aeruginosa strain MCC 2081

Alginate lyases are potential agents for disrupting alginate-rich Pseudomonas biofilms in the infected lungs of cystic fibrosis patients but there is as yet no clinically approved alginate lyase that can be used as a therapeutic. We report here the endolytic alginate lyase activity of a recombinant Cellulophaga algicola alginate lyase domain (CaAly) encoded by a gene that also codes for an N-terminal carbohydrate-binding module, CBM6, and a central F-type lectin domain (CaFLD). CaAly degraded both polyM and polyG alginates with optimal temperature and pH of 37°C and pH 7, respectively, with greater preference for polyG. Recombinant CaFLD bound to fucosylated glycans with a preference for H-type 2 glycan motif, and did not have any apparent effect on the enzyme activity of the co-associated alginate lyase domain in the recombinant protein construct, CaFLD_Aly. We assessed the potential of CaAly and other alginate lyases previously reported in published literature to inhibit biofilm formation by a clinical strain, Pseudomonas aeruginosa MCC 2081. Of all the alginate lyases tested, CaAly displayed most inhibition of in vitro biofilm formation on plastic surfaces. We also assessed its inhibitory ability against P. aeruginosa 2081 biofilms formed over a monolayer of A549 lung epithelial cells. Our study indicated that CaAly is efficacious in inhibition of biofilm formation even on A549 lung epithelial cell line monolayers.

Glycan binding profile of a fucolectin-related protein (FRP) encoded by the SP2159 gene of Streptococcus pneumoniae

The recombinant fucolectin-related protein (FRP) of unknown function, encoded by the SP2159 gene of Streptococcus pneumoniae, was expressed in E. coli. In this study, its glycan-recognition epitopes and their binding potencies were examined by enzyme-linked lectinosorbent and inhibition assays. The results indicate that FRP reacted strongly with human blood group ABH and l-Fucα1→2-active glycotopes and in their polyvalent (super) forms. When expressed by mass relative potency, the binding affinities of FRP to poly-l-Fucα1→glycotopes were about 5.0 × 10⁵ folds higher than that of the mono-l-Fucα1→glycotope form. This unique binding property of FRP can be used as a special tool to differentiate complex forms of l-Fucα1→2 and other forms of glycotopes.