Dihydropyridine-sensitive calcium channels in cardiac and skeletal muscle membranes: studies with antibodies against the. cap alpha. subunits

Journal Article · Tue Aug 25 04:00:00 EDT 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00391a046· OSTI ID:5943045

Takahashi, M; Catterall, W A

Polyclonal antibodies (PAC-2) against the purified skeletal muscle calcium channel were prepared and shown to be directed against ..cap alpha.. subunits of this protein by immunoblotting and immunoprecipitation. These polypeptides have an apparent molecular weight of 162,000 without reduction of disulfide bonds. Under conditions where the functional properties of the purified skeletal muscle calcium channel are retained, ..beta.. subunits (M/sub r/ 50,000) and lambda subunits (M/sub r/ 33,000) are coprecipitated, demonstrating specific noncovalent association of these three polypeptides in the purified skeletal muscle channel. PAC-2 immunoprecipitated cardiac calcium channels labeled with (/sup 3/H)isopropyl 4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-2,6-dimethyl-5-(methoxycarbonyl)pyridine-3-carboxylate ((/sup 3/H)PN200-110) at a 3-fold higher concentration than skeletal muscle channels. Preincubation with cardiac calcium channels blocked only 49% of the immunoreactivity of PAC-2 toward skeletal muscle channels, indicating that these two proteins have both homologous and distinct epitopes. The immunoreactive component of the cardiac calcium channel was identified by immunoprecipitation and polyacrylamide gel electrophoresis as a polypeptide with an apparent molecular weight of 170,000 before reduction of disulfide bonds and 141,000 after reduction, in close analogy with the properties of the ..cap alpha../sub 2/ subunits of the skeletal muscle channel. The calcium channels were radiolabeled with /sup 32/P and /sup 125/I. It is concluded that these two calcium channels have a homologous, but distinct, ..cap alpha.. subunit as a major polypeptide component.

• Research Organization: Univ. of Washington, Seattle
• OSTI ID: 5943045
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:17; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALI METAL COMPOUNDS
ATP
AZINES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CARDIOVASCULAR SYSTEM
CELL CONSTITUENTS
CELL MEMBRANES
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
ELECTROPHORESIS
HALIDES
HALOGEN COMPOUNDS
HEART
HETEROCYCLIC COMPOUNDS
INORGANIC PHOSPHORS
INTERMEDIATE MASS NUCLEI
IODIDES
IODINE 125
IODINE COMPOUNDS
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
MEMBRANE TRANSPORT
MEMBRANES
MOLECULAR STRUCTURE
MUSCLES
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PEPTIDES
PHOSPHORS
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
POLYPEPTIDES
PROTEINS
PYRIDINES
RADIOISOTOPES
SODIUM COMPOUNDS
SODIUM IODIDES
TRACER TECHNIQUES
TRITIUM COMPOUNDS