G-GECO1.2 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-GECO1.2 was derived by mutagenesis of GCaMP3, containing in addition the mutations K69E, N77Y, D86G, K119I, L173Q, D260G, S404G and E430V (PMID:21903779). For detailed kinetic and spectral properties, see PMID:21903779.