A mutation was engineered in exon 76 to change valine codon 3598 to a lysine codon (p.V3598K) and a loxP site flanked neomycin resistance gene cassette was inserted into intron 76. The neo cassette was removed through subsequent cre-mediated recombination. The mutation in the calmodulin (CaM) binding domain significantly increases binding affinity of the encoded peptide to calmodulin. (J:308964)