δ-FlincG is a genetically encoded fluorescent sensor for cGMP. It contains two tandem cGMP binding sites (amino acids 77-356 of the β isoform of the Bos taurus PRKG1 gene, VGNC:33340), followed by circularly permuted EGFP (cpEGFP), with a tail of 17 additional amino acids after the cpEGFP sequence (PMID:18165313). Binding of cGMP to the two cGMP binding sites results in conformational changes that increase fluorescence intensity of cpEGFP (PMID:18165313).