A leucine zipper stabilizes the pentameric membrane domain of phospholamban and forms a coiled-coil pore structure.
Phospholamban is a phosphoprotein regulator of cardiac sarcoplasmic reticulum which is phosphorylated in response to beta-adrenergic stimulation. Previous results have shown that phospholamban forms Ca2+-selective channels in lipid bilayers. The channel-forming domain has been localized to amino acid residues 26-52, which form a stable pentameric, helical structure. The specific residues responsible for stabilizing the pentameric membrane domain of phospholamban have been identified by mutational analysis. Residues 26-52 were individually mutated to Ala or Phe, and the ability of the resulting mutant to form a pentamer or other oligomer was assessed by SDS-polyacrylamide gel electrophoresis analysis. Replacement of Leu37, Ile40, Leu44, Ile47, or Leu51 by Ala prevented pentamer formation, indicating their essential involvement in the oligomeric assembly. The heptad repeats, and 3-4-residue spacing of the essential amino acids suggest that residues 37-52 adopt a pentameric coiled-coil structure stabilized by a leucine zipper motif formed by the close packing of Leu37, Ile40, Leu44, Ile47, and Leu51. The resulting symmetric structure contains a central pore defined by the hydrophobic surface of the five stabilizing leucine zippers, which are oriented to the interior and form the backbone of the pentamer.[1]References
- A leucine zipper stabilizes the pentameric membrane domain of phospholamban and forms a coiled-coil pore structure. Simmerman, H.K., Kobayashi, Y.M., Autry, J.M., Jones, L.R. J. Biol. Chem. (1996) [Pubmed]
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