Revealing the allosterome: Systematic identification of metabolite-protein interactions

Small molecule allostery modifies protein function but is not easily discovered. We introduce mass spectrometry integrated with equilibrium dialysis for the discovery of allostery systematically (MIDAS), a method for identifying physiologically relevant, low-affinity metabolite-protein interactions using unmodified proteins and complex mixtures of unmodified metabolites. In a pilot experiment using five proteins, we identified 16 known and 13 novel interactions. The known interactions included substrates, products, intermediates, and allosteric regulators of their protein partners. MIDAS does not depend upon enzymatic measurements, but most of the new interactions affect the enzymatic activity of the protein partner. We found that the fatty acid palmitate interacts with both glucokinase and glycogen phosphorylase. Further characterization revealed that palmitate inhibited both enzymes, possibly providing a mechanism for sparing carbohydrate catabolism when fatty acids are abundant.