Homologous cardiac calcium pump regulators phospholamban and sarcolipin adopt distinct oligomeric states in the membrane

Figures

• 

  Fig. 1. Molecular architecture of the PLN and SLN pentamers in a lipid bilayer. (A) A representative structure from the NMR ensemble of the PLN pentamer (PDB: 2kyv [11]). (B) The three-dimensional structure of the SLN pentamer we used as a starting point for the MD simulations. Distributions of the tilt angle of the transmembrane domain of each (C) PLN and (D) SLN protomer were calculated from the MD trajectories using the pentamer as a starting structure. The dashed line indicates the average tilt angle calculated for all protomers using the initial structures of the PLN and SLN pentamers. In all cases, individual protomers M1 (red), M2 (blue), M3 (green), M4 (magenta), and M5 (orange) are shown in a cartoon representation. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

• 

  Fig. 2. Structures of the PLN and SLN pentamers. (A) Structures of the PLN pentamer at the end of the 1-µs MD trajectory. (B) Configuration of the SLN pentamer at the end of each MD replicate. In all cases, the structures are oriented so that the z-axis is parallel to the membrane plane normal and viewed from the cytosolic side. Individual protomers M1 (red), M2 (blue), M3 (green), M4 (magenta), and M5 (orange) are shown in a cartoon representation. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

• 

  Fig. 3. Stability of the leucine zipper, measured by key interresidue distance distributions across all protomer–protomer interfaces. We show selected interresidue distances calculated from replicate 1 of PLN and replicates 2 and 4 of SLN. The dashed brown line indicates the average distance calculated from the initial model of the SLN pentamer as well as the NMR structure of the PLN pentamer. Each interface is labeled using the nomenclature used in Fig. 1, Fig. 2. The representations on the left panel show the PLN and SLN pentamers (cartoon representation) and the location of the leucine zipper residues (van der Waals spheres). These structures also illustrate stable and disrupted leucine zippers.

• 

  Fig. 4. Oligomerization of PLN and SLN in mouse hearts and human iPSC-derived cardiomyocytes (iPSC-CM) revealed by Western blot analysis. (A) Western blot analysis of mouse ventricles and ventricle-like human iPSC-derived cardiomyocytes showed the presence of PLN pentamers in both species. (B) Representative structures of the PLN pentamer (cartoon representation) show the formation of stable leucine zippers (purple spheres). (C) We detected the presence of SLN dimers, trimers, and pentamers in mouse atria, whereas dimers and pentamers were found in atria-like human iPSC-derived cardiomyocytes. (D) MD simulations of the SLN oligomers agree with experiments and revealed the formation of structurally stable dimeric, trimeric and pentameric states. Individual protomers are shown in a cartoon representation, and leucine zippers are shown as spheres. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)