15N Solid-state NMR spectroscopic studies on phospholamban at its phosphorylated form at Ser-16 in aligned phospholipid bilayers

Wild-type phospholamban (WT-PLB) is a pentameric transmembrane protein that regulates the cardiac cycle (contraction and relaxation). From a physiological prospective, unphosphorylated WT-PLB inhibits sarcoplasmic reticulum ATPase activity: whereas, its phosphorylated form relieves the inhibition in a mechanism that is not completely understood. In this study, site-specifically N-15-Ala-11- and N-15-Leu-7-labeled WT-PLB and the corresponding phosphorylated forms (P-PLB) were incorporated into 1,2-dioleoyl-sn-glycero-3-phosphocholine/2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPC/DOPE) mechanically oriented lipid bilayers. The aligned N-15-labeled Ala-11 and Leu-7 WT-PLB samples show N-15 resonance peaks at approximately 71 ppm and 75 ppm, respectively, while the corresponding phosphorylated forms P-PLB show N-15 peaks at 92 ppm and 99 ppm, respectively. These N-15 chemical shift changes upon phosphorylation are significant and in agreement with previous reports, which indicate that phosphorylation of WT-PLB at Ser-16 alters the structural properties of the cytoplasmic domain with respect to the lipid bilayers. Published by Elsevier B.V.