GCaMP5A is a genetically encoded fluorescent Ca[2+] indicator that consists of the calmodulin-binding peptide M13, a circularly permuted green fluorescent protein and calmodulin. GCaMP5A was derived by mutagenesis of GCaMP3, containing in addition the mutation D380Y (FBrf0219564). For detailed kinetic and spectral properties and a comparison of GCaMP5A with other GCaMP series sensors, see FBrf0219564.