Mutational analysis of affinity and selectivity of kringle-tetranectin interaction - Grafting novel kringle affinity onto the tetranectin lectin scaffold

C-type lectin-like domains are found in many proteins, where they mediate b inding to a wide diversity of compounds, including carbohydrates, lipids, a nd proteins. The binding of a C-type lectin-like domain to a ligand is ofte n influenced by calcium. Recently, we have identified a site in the C-type lectin-like domain of tetranectin, involving Lys-148, Glu-150, and Asp-165, which mediates calcium-sensitive binding to plasminogen kringle 4. Here, w e investigate the effect of conservative substitutions of these and a neigh boring amino acid residue. Substitution of Thr-149 in tetranectin with a ty rosine residue considerably increases the affinity for plasminogen kringle 4, and, in addition, confers affinity for plasminogen kringle 2. As shown b y isothermal titration calorimetry analysis, this new interaction is strong er than the binding of wild-type tetranectin to plasminogen kringle 4. This study provides further insight into molecular determinants of importance f or binding selectivity and affinity of C-type lectin kringle interactions.