G-CEPIA1 is a genetically encoded fluorescent Ca[2+] indicator. It consists of the M13 calmodulin-binding peptide, a circularly permuted green fluorescent protein and calmodulin. G-CEPIA1 was derived by replacing the calmodulin sequence of G-GECO1.1 with that of CEPIA1 (PMID:24923787). For detailed kinetic and spectral properties and a comparison of G-CEPIA1 with other CEPIA series sensors, see PMID:24923787.