Figure 1.

Schematic representation of (a) structure and working mechanism of Pink Flamindo and (b) protein kinase A (PKA)-based 3′-5′-cyclic adenosine monophosphate (cAMP) sensor cAMP universal tag for imaging experiments (CUTie). Pink Flamindo is a single fluorescent protein (FP)-based sensor. Binding of cAMP enhances fluorescence and vice versa. Without cAMP, two fluorescent proteins are apart from each other (low Föster resonance energy transfer (FRET)), whereas two FPs are close to each other in the presence of cAMP (high FRET).