UAS regulatory sequences drive expression of the genetically encoded A-kinase activity reporter "AKAR3" (see PMID:16895723). "AKAR3" consists of two fluorescent proteins (ECFP and a Venus variant that is circularly permuted at residue E172) that are separated by sequence encoding a phospho-binding domain (forkhead associated domain 1 (FHA1) from the Saccharomyces cerevisiae RAD53 gene) and a protein kinase A (PKA) substrate domain (LRRATLVD). When phosphorylated by PKA, the PKA substrate domain interacts with the phospho-binding domain, increasing the fluorescence resonance energy transfer (FRET) between the two fluorophores. The AKAR3 protein is tagged at the N-terminal end with a myristoylation signal (Tag:Myr(Src64B)).