A novel reporter system, which is applicable to the (19)F NMR investigation of protein interactions, is presented. This approach uses 2-F-labeled maltose as a spy ligand to indirectly probe protein-ligand or protein-protein interactions of proteins fused or tagged to the maltose-binding protein (MBP). The key feature is the simultaneous NMR observation of both (19)F NMR signals of gluco/manno-type-2-F-maltose-isomers; one isomer (α-gluco-type) binds to MBP and senses the protein interaction, and the nonbinding isomers (β-gluco- and/or α/β-manno-type) are utilized as internal references. Moreover, this reporter system was used for relative affinity studies of fluorinated and nonfluorinated carbohydrates to the maltose-binding protein, which were found to be in perfect agreement with published X-ray data. The results of the NMR competition experiments together with the established correlation between (19)F chemical shift data and molecular interaction patterns, suggest valuable applications for studies of protein-ligand interaction interfaces.
Keywords: 19F NMR; fluorination; maltose derivatives; maltose-binding protein (MBP); protein interaction.