CUTie2 is a genetically-encoded FRET sensor for cGMP. It is based on the cyclic nucleotide-binding domain (CNBD) of the Homo sapiens PRKG1 gene (HGNC:9414) and contains the FRET pair YFP and CFP. The YFP protein (flanked by linkers) is inserted into the 4-5 loop of the PRKG1 CNBD (replacing amino acids DSPSE) and CFP is fused directly downstream of the CNBD. Binding of cGMP to the PRKG1 CNBD results in a conformational change, resulting in a change in FRET efficiency (PMID:33778003).