FIGURE 6.

Phospholemman multimers in cardiac muscle. A, characterization of PLM from WT and KI animals on standard and Phos-Tag SDS-PAGE. The mobility of molecular mass standards is indicated alongside the immunoblots. Unphosphorylated (0P, immunoreactive with total PLM antibody only) and singly (1P) and doubly (2P) phosphorylated states (immunoreactive with Ser⁶³ (S63) phosphospecific antibody) are resolved on Phos-Tag PAGE. 3SA PLM migrates entirely as unphosphorylated in Phos-Tag gels. B, Ser⁶³-phosphorylated PLM was immunoprecipitated from WT, heterozygous KI (HET), and homozygous KI hearts under co-immunoprecipitation (Co-IP) and immunoprecipitation (IP) conditions. Purification of unphosphorylated PLM (0P) in co-immunoprecipitation reactions confirms the existence of interactions between WT and 3SA/unphosphorylated PLM.