Isothermal titration calorimetry (ITC)

All peptides were synthesized by GL Biochem (Shanghai) Ltd. and were dissolved in water as a stock of 5–12 mM, with the pH of stock solutions adjusted to pH 7.5. Peptides and concentrated proteins were diluted with ITC buffer (20 mM Tris, pH 7.5 and 150 mM NaCl). ITC experiments were performed by titrating 2 μl of peptide (1.2–1.5 mM) into cells containing 50 µM proteins on MicroCal (Malvern Panalytical, UK) at 25°C, with a spacing time of 160 s and a reference power of 10 µCal/s. Control experiments were performed by injection of peptides into buffer. Binding isotherms were plotted, analyzed and fitted in a one-site binding model by MicroCal PEAQ-ITC Analysis Software (Malvern Panalytical, UK) after subtraction of the respective controls. The dissociation constants (Kds) were determined from a minimum of two experiments (mean ± SD). The ITC binding curves are shown in Supplementary file 1.