FIGURE 1.

(a) Three‐dimensional structure of the tandem of PDZ1 (in red) and PDZ2 (in green) of X11 (PDB:1u3b). Residues W676 and I767 are shown in sticks. In this work, I767 was mutated to W to spectroscopically follow the folding and unfolding reaction of PDZ2 domain. (b) Equilibrium unfolding curves of isolated PDZ1 domain (in red), isolated PDZ2 domain (in green) and of the tandem construct (in black). All the three curves were fitted with a sigmoidal function, highlighting the cooperative nature of the unfolding reaction in all the constructs.