Département de chimie moléculaire

CBMs (carbohydrate-binding modules) are a class of polypeptides usually assocd. with carbohydrate-active enzymic 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 $\alpha$(2,3)-linked sialosides, which was confirmed and quantified by calorimetric studies. The CBM40 binds to $\alpha$(2,3)-sialyl-lactose with a Kd of ∼30 $μ$M, 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 obsd. 6-11-fold binding increases due to the avidity affect. The structures of the CBM, resolved by X-ray crystallog., in complex with $\alpha$(2,3)- or $\alpha$(2,6)-sialyl-lactose explain its binding specificity and unusually strong binding. [on SciFinder(R)]