ABSTRACT
Most binding studies deal with attachment of small ligands (drugs, hormones, ions or other endo- and xenobiotics) to proteins. The molecular topology of the most common drug acceptors suggests that interacting proteins are usually integrated in intra- or extracellular surfaces of membranes, building functional units of true receptors or receptor-like structures, ion channels and pumps. Besides affinity, reversibility, stoichiometry and saturability, the principal functional criteria for classification of protein binding sites include stereoselectivity and tissue- and/or species-specificity. Information on the stoichiometry of biomolecular interactions involving, example, immunoglobulins, streptavidin, lectins or enzymes, implicates their specificity and affords insight into the network of interlinked molecular mechanisms essential for a living organism. Chiral recognition properties of protein targets, distinguishing the three-dimensional conformation of an attaching pharmacophore, are responsible for quantitative or qualitative differences in affinity and/or efficacy of individual drug enantiomers.
