RCaMP2 is a genetically encoded red fluorescent Ca[2+] indicator. It is a fusion protein composed of 'ckkap-WL' (a sequence that can bind Ca[2+]-bound calmodulin - this is a hybrid of sequence derived from CaMKK-α and CaMKK-β), a circularly permuted red fluorescent protein and calmodulin. The circularly permuted fluorescent protein is based on mApple. A number of amino acid substitutions (N380S, D381Y, T382R and S384T) have been introduced into the calmodulin sequence relative to the R-CaMP1.07 parent variant, resulting in faster rise and decay times and increased response amplitudes. Excitation and emission peaks are 565nm and 583nm (PMID:25419959).