R-GECO1 is a genetically encoded fluorescent Ca[2+] indicator. It consists of a calmodulin-binding peptide, a circularly permuted red fluorescent protein and calmodulin. The circularly permuted fluorescent protein is interrupted at residue 145, and is based on mApple, with the additional mutations T47A, L60P, E61V, S63V, E64S, R81G, K83R, Y134C, M158L, N164D, V228A, S290P, I366F, K380N, S404G, N414D and E430V relative to the starting M13-cp-mApple-Cam fusion (PMID:21903779). For detailed kinetic and spectral properties, see PMID:21903779.