Isothermal titration calorimetry (ITC) analysis of either SKH (A), Mg²⁺ATP (B), or Mg²⁺ADP (C) binding to MtSK.

The top graphs show raw data of the heat pulses resulting from titration of MtSK (100 µM for ATP and ADP, and 130 µM for SKH and S3P) in the calorimetric cell with one injection of 0.5 µL of ligand followed by 17 injections of 2.26 µL injection. The injection syringe (39 µL) contained either ATP or ADP at 6 mM, or SKH and S3P at 4.2 mM. The bottom graphs show the integrated heat pulses, normalized per mol of injectant as a function of the molar ratio (ligand/MtSK concentration). These binding curves were best fitted to a single set of sites model equation.