Here we described C-type lectin-oriented surfaces for SPR analysis. They allow the preservation of receptor topology, accessibility of binding sites, better evaluation of high avidity compounds and assessment of multivalent effect at cell surface.
CBMs (carbohydrate-binding modules) are a class of polypeptides usually associated with carbohydrate-active enzymatic sites. We have characterized a new member of the CBM40 family, coded from a section of the gene NanI from Clostridium perfringens Glycan arrays revealed its preference towards α(2,3)-linked sialosides, which was confirmed and quantified by calorimetric studies. The CBM40 binds to α(2,3)-sialyl-lactose with a Kd of ∼30 μM, the highest affinity value for this class of proteins. Inspired by lectins' structure and their arrangement as multimeric proteins, we have engineered a dimeric form of the CBM, and using SPR (surface plasmon resonance) we have observed 6-11-fold binding increases due to the avidity affect. The structures of the CBM, resolved by X-ray crystallography, in complex with α(2,3)- or α(2,6)-sialyl-lactose explain its binding specificity and unusually strong binding.
Chronic colonization of lungs by opportunist bacteria is the major cause of mortality for cystic fibrosis patients. Among these pathogens, Burkholderia cenocepacia is responsible for cepacia syndrome, a deadly exacerbation of infection that is the main cause of poor outcomes of lung transplantation. This bacterium contains three soluble carbohydrate‐binding proteins, including the B. cenocepacia lectin A (BC2L‐A), which is proposed to bind to oligomannose‐type N‐glycan structures to adhere to host tissues. In this work, several mannosylated glycoclusters and glycodendrimers with valencies ranging from four to 24 were prepared and their interactions with BC2L‐A were thermodynamically characterized by isothermal titration calorimetry. The results show that a 24‐valent structure binds to BC2L‐A at nanomolar concentration, which makes this compound the highest affinity monodisperse ligand for this lectin.
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