An investigation of the binding site of alpha 2u-globulin using isotopically labeled ligands and inverse nuclear magnetic resonance techniques.

A series of isotopically labeled ligands were bound to the protein alpha 2u-globulin. These protein complexes were studied using 13C, 19F, and selective inverse detection NMR experiments to determine chemical shifts and nuclear Overhauser effect correlations for the labeled sites of the ligands. The NMR data indicate that the labeled portions of the ligands are located in a highly aromatic region of the alpha 2u-globulin binding pocket. Molecular modeling based on the NMR data and a medium resolution X-ray crystal structure of alpha 2u-globulin predicts a model for ligand binding which is consistent with experimental observations and calculated ring current effects. Conformational changes in the aromatic region of the binding site upon binding these ligands in solution may be supported by this model.