Evidence for a phosphorylation-induced conformational change in phospholamban cytoplasmic domain by CD analysis

Phospholamban (PLB), an integral membrane protein of cardiac sarcoplasmic reticulum (SR), is described as the regulator of the Ca(2+)-ATPase pump, via its phosphorylation-dephosphorylation of Ser-16. Recently it has been shown that a direct interaction between the N-terminal hydrophilic domain of PLB and Ca(2+)-ATPase may be one of the mechanisms of regulation. In order to show that this interaction could be modulated by a phosphorylation-induced conformational change in PLB, we ran CD studies on the synthetic peptide PLB(2-33) in its phosphorylated and non-phosphorylated forms, at various pHs, concentrations and in the absence or presence of trifluoroethanol. The results show a clear difference in structure of the phosphorylated and non-phosphorylated peptide.