The inter-ligand Overhauser effect: a powerful new NMR approach for mapping structural relationships of macromolecular ligands.

NMR experiments that transfer conformational information from the bound to the uncomplexed state via exchange have been utilized for many years. It is demonstrated here that inter-ligand NOEs ('ILOEs'), which exist in ternary complexes with enzymes or other macromolecular receptors, can be transferred via exchange to pairs of uncomplexed ligands. This approach is illustrated by studies of glycolate + NAD+ in the presence of porcine heart lactate dehydrogenase, and by glucose-6-phosphate + NADPH in the presence of L. mesenteroides glucose-6-phosphate dehydrogenase. This strategy opens up a general methodology for exploring the active sites of enzymes and for the development of artificial ligands which can function as inhibitors, or more generally as modifiers of protein function.