Subunit Structure of Dihydropyridine-Sensitive Calcium Channels from Skeletal Muscle

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 84; no. 15; pp. 5478 - 5482
• Main Authors: Takahashi, Masami, Seagar, Michael J., Jones, Jean F., Bernhard F. X. Reber, Catterall, William A.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01-08-1987; National Acad Sciences
• Subjects: Animals; Antibodies; Biological and medical sciences; Calcium; Calcium - metabolism; Calcium Channel Blockers - pharmacology; Calcium channels; Cell physiology; Detergents; dihydropyridine; Disulfides; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; Gels; Ion Channels - ultrastructure; Lectins; Lentils; Macromolecular Substances; Molecular and cellular biology; Muscles - analysis; Neurotransmission; Peptides - analysis; Phosphorylation; Protein Conformation; Rabbits; Skeletal muscle; Calcium; Molecular structure; Rabbit; Molecular interaction; Ionic channel; Lagomorpha; Striated muscle; Subunit; Vertebrata; Mammalia; Animal; Molecular model; Quaternary structure; Membrane channel
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.84.15.5478

Purified dihydropyridine-sensitive calcium channels from rabbit transverse-tubule membranes consist of three noncovalently associated classes of subunits: α (167 kDa), β (54 kDa), and γ (30 kDa). Cleavage of disulfide bonds reveals two distinct α polypeptides and an additional component, δ . The α 1 subunit, a 175-kDa polypeptide that is not N-glycosylated, contains the dihydropyridine binding site, cAMP-dependent protein kinase phosphorylation site(s), and substantial hydrophobic domain(s). α 2, a 143-kDa glycoprotein, has none of the properties characteristic of α 1 but binds lectins and contains about 25% N-linked carbohydrate. α 2 is disulfide-linked to δ , a 24- to 27-kDa glycopeptide. β (54 kDa) contains a cAMP-dependent phosphorylation site but is not N-glycosylated and does not have a hydrophobic domain. γ (30 kDa) has a carbohydrate content of about 30% and extensive hydrophobic domain(s). Precipitation with affinity-purified anti-α 1 antibodies or α 2-specific lentil lectin-agarose demonstrated that α 1α 2β γ δ behaves as a complex in the presence of digitonin or 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, whereas the α 2δ complex dissociates from α 1β γ in the presence of Triton X-100. A model for subunit interaction and membrane insertion is proposed on the basis of these observations.