Location of mutations and results of binding measurements. (A) Structure of the CBFβ–Runt domain–DNA complex (PDB code 1h9d) with Runt domain amino acids mutated in the Roudaia et al (orange) and Kwok et al (red) studies indicated.^1,2  CBFβ is indicated in blue; Runt domain in green; and DNA in pink. (B) Results of isothermal titration calorimetry (ITC) measurements of the binding of CBFβ to wild-type Runt domain, M106V Runt domain, and A107T Runt domain. Measurements for the M106V mutant were carried out at 22°C, as done in the Roudaia et al study. Measurements for the A107T mutant were carried out at 30°C as a result of very low signals at 22°C for this mutant, precluding an accurate measurement. The wild-type Runt domain has also been measured at this temperature to provide an accurate comparison between the 2. The enthalpy of the reaction changes from exothermic to endothermic upon going from 22°C to 30°C, resulting in the mirror image appearance of the data for the wild-type Runt domain at the 2 different temperatures.