The structural topology of wild‐type phospholamban in oriented lipid bilayers using 15 N solid‐state NMR spectroscopy

Abstract

For the first time, 15 N solid‐state NMR experiments were conducted on wild‐type phospholamban (WT‐PLB) embedded inside mechanically oriented phospholipid bilayers to investigate the topology of its cytoplasmic and transmembrane domains. 15 N solid‐state NMR spectra of site‐specific 15 N‐labeled WT‐PLB indicate that the transmembrane domain has a tilt angle of 13° ± 6° with respect to the POPC (1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐phosphocholine) bilayer normal and that the cytoplasmic domain of WT‐PLB lies on the surface of the phospholipid bilayers. Comparable results were obtained from site‐specific 15 N‐labeled WT‐PLB embedded inside DOPC/DOPE (1,2‐dioleoyl‐ sn ‐glycero‐3‐phosphocholine/1,2‐dioleoyl‐ sn ‐glycero‐3‐phosphoethanolamine) mechanically oriented phospholipids' bilayers. The new NMR data support a pinwheel geometry of WT‐PLB, but disagree with a bellflower structure in micelles, and indicate that the orientation of the cytoplasmic domain of the WT‐PLB is similar to that reported for the monomeric AFA‐PLB mutant.