Interaction of calcineurin with its activator, chlorogenic acid revealed by spectroscopic methods

Chlorogenic acid (CHA) has been proved to be an activator of calcineurin (CN) in our previous research. In this study, the activation of single chain calcineurin (BA) by CHA, their interaction and concomitant changes in protein conformation were studied using fluorescence and Fourier transform infrared spectroscopy. Evidence is present that binding of CHA to CN is responsible for the stimulation of enzyme and results in structural changes. Aromatic residues reorient into new environments upon binding of CHA, the binding constant for the reaction was (2.76 +/- 0.64) x 10(4) M(-1) by one binding site, which indicated that CHA bound to BA statically and the change of secondary structure was mainly due to reduced alpha-helical content and increased beta-turns. The results obtained in this study should be useful for understanding the molecular mechanisms underlying the interactions between CN and its activators.