Figure 4.

Isothermal Titration Calorimetry of WT and Truncated CaBP2

(A) Trace of the calorimetric titration of 5 μl aliquots (after one initial injection of 2 μl) of 5 mM CaCl₂ into 1.3 ml of 110 μM recombinant WT apo-CaBP2. A robust endothermic binding reaction was observed.

(B) Trace of the calorimetric titration of 5 μl aliquots (after one initial injection of 2 μl) of 5 mM CaCl₂ into 1.3 ml of 114 μM recombinant truncated apo-CaBP2 (MT CaBP2 [ΔEF hands 3 and 4]). In contrast to the WT apo-CaBP2, the truncated protein leads to a weaker and exothermic reaction.

(C) Trace of the blank titration curve for both experiments A and B with the same parameters but without protein in the sample cell.