GCaMP6-210 is a genetically encoded fluorescent Ca[2+] indicator with relatively low affinity for Ca[2+] (210 μM K[[d]]]) to match resting [Ca2+] in axonal endoplasmic reticulum but with a high responsiveness upon binding to Ca[2+]. It consists of the calmodulin-binding peptide M13, a circularly permuted green fluorescent protein and calmodulin. GCaMP6-210 contains the following mutations relative to GCaMP3 : K78H, T302L, R303P, A317E, D324G, D360G, D380Y, T381R, S383T, R392G, D397G. For detailed kinetic and spectral properties and a comparison of GCaMP6-210 with other GCaMP series sensors, see PMID:28162809.