19F NMR evidence for interactions between the c‐AMP binding sites on the c‐AMP receptor protein from E. coli

Abstract
The 19F NMR spectra of 3‐fluorotyrosine containing c‐AMP receptor protein (CRP) from E. coli have been recorded in the presence of increasing amounts of c‐AMP. One of the signals (from Tyr B) shifts upfield by 0.6 ppm in the presence of excess c‐AMP and shows both slow and fast exchange behaviour during the titration. This is evidence for interactions between the two c‐AMP binding sites on the CRP dimer leading to different dissociation rate constants (≤ 75 s−1; ≥ 350 s−1) for complexes containing one and two c‐AMP molecules.