Phosphorylation of the serine amino acid at 2808 modifies the activity of this gene product. A modified exon 55 containing a serine to alanine (S2808A) mutation and a translationally silent Mlu-I restriction site replaced the endogenous exon. A loxP-flanked neomycin cassette was also inserted downstream of the modified exon and was subsequently removed by mating founder mice with EIIa-cre transgenic mice. Mutant protein expression was confirmed in homozygote cardiomycotes by detection of protein with an Ryr2-specific antibody and a lack of signal with the phospho-specific RyR2-pS2808 antibody.