Thermodynamic analysis of Tiam2 PDZ/Caspr4 peptide interactions determined by ITC. (A) Representative thermograms and integrated titration curves are shown for the Caspr4 ligand bound to Tiam2 WT, E979K/F982L, M978L/V987L, and QM PDZ domains. Protein and ligand concentrations used in the experiments are indicated. (B) Average thermodynamic parameters for Tiam2 PDZ/Caspr4 interactions at 25°C are shown. The change in enthalpy (ΔH), association constant (Ka), and stoichiometry (n) were fit by nonlinear least squares analysis using a single-site binding model in ORIGIN software. Each parameter represents the mean and SD from two to three technical replicates.