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.
Simmerman
H K
HK
Repligen Corporation, Cambridge, Massachusetts 02139, USA.
Kobayashi
Y M
YM
Autry
J M
JM
Jones
L R
LR
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D015220:Calcium Channels / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D003001:Cloning, Molecular; D004355:Drug Stability; D004591:Electrophoresis, Polyacrylamide Gel; D007532:Isoleucine; D007930:Leucine; D016350:Leucine Zippers; D046911:Macromolecular Substances; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010649:Phenylalanine; D017354:Point Mutation; D014176:Protein Biosynthesis; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D015183:Restriction Mapping; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic; D000099211:Phospholamban
D000251:Adenosine Triphosphatases; D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D007532:Isoleucine; D007930:Leucine; D046911:Macromolecular Substances; D010649:Phenylalanine; D011994:Recombinant Proteins; D000099211:Phospholamban