Figure 3.

Intrinsically unfolded protein as input domain for FRET sensors. In the absence of Mg²⁺ the molten-globule state of the N-terminal part of HsCen3 results in little FRET. Binding of Mg²⁺ induces formation of a well-defined EF-hand fold, which decreases the distance between Cerulean and Citrine and thus increases FRET. Figure adapted from [55].