Stoichiometry Regulates Macromolecular Recognition and Supramolecular Assembly: Examples From Lectin-Glycoconjugate Interaction

Lectin-glycoconjugate interactions are essential for numerous cellular and extracellular events. Binding stoichiometry is one of several factors that regulate the initiation and outcome of lectin-mediated biological functions. Therefore, the knowledge of accurate stoichiometry of glycoconjugate binding is pivotal for delineating the molecular mechanism of lectin-dependent processes. Quantitative precipitation and isothermal titration calorimetry can reliably determine the stoichiometry of glycoconjugate recognition by lectins. Stoichiometry plays important roles in affinity enhancement and it influences the structures of lectin-glycoconjugate cross-linked complexes. Correct stoichiometry helped reveal that the binding epitopes (glycans) on multi- and polyvalent glycoconjugates possess decreasing microscopic binding affinities for lectins and the binding of lectin involves an internal diffusion process called "bind and jump." Interestingly, in certain cases, stoichiometry is unable to regulate affinity enhancement, binding thermodynamics, kinetics of cross-linking, and the lattice structures of the cross-linked complexes.