GCaMP2 is a genetically encoded fluorescent Ca[2+] indicator. It is a fusion protein composed of an N-terminal 35 residue RSET leader sequence (which includes Tag:polyHis), the calmodulin-binding peptide M13, a circularly permuted fluorescent protein and calmodulin. The circularly permuted fluorescent protein is interrupted at residue 145, and is based on EGFP, with the additional mutations V163A, S175G, D180Y, A206K and V93I (PMID:16537386). For detailed kinetic and spectral properties, see PMID:16537386. For a comparison of GCaMP2 with other GCaMP series sensors, see FBrf0219564.