Subunits of purified calcium channels: a 212-kDa form of alpha 1 and partial amino acid sequence of a phosphorylation site of an independent beta subunit.

Abstract

Antibodies prepared against peptides CP2, CP4, and CP5, which occur within the first 1522 amino acid residues of the al subunit of dihydropyridine-sensitive skeletal muscle calcium channels, specifically recognized a 175-kDa form of the a, subunit in immunoblots and immunoprecipitation experiments. In contrast, antibodies prepared against peptide CP1, which represents the C-terminal 18 amino acid residues predicted by cloning and sequence analysis of the a, subunit, recognized a minor, previously undescribed 212-kDa protein, which is the size predicted for the full length of the al subunit from cDNA cloning [Tanabe, T., Takeshima, H., Mikami, A., Flockerzi, V., Takahashi

The devapamil‐binding site of the purified skeletal muscle receptor for organic‐calcium channel blockers is modulated by micromolar and millimolar concentrations of Ca2+

“…Additional, unidentified proteins or phospholipids are not required for devapamil binding and its allosteric regulation. This is an important conclusion, since previous work suggested the following: (a) the purified CaCB receptor binds devapamil with a low-affinity and stoichiometry of 1 : 1 [25, 261; (b) potentially only the 212-kDa a1 subunit [50] which is present in skeletal muscle [51] binds phenylalkylamines with high affinity and not the commonly purified 165-kDa a1 subunit; (c) inhibition of a reconstituted skeletal muscle calcium channel by a phenylalkylamine requires an additional protein [52]. The following evidence argues in favor of a 165-kDa a1 subunit.…”

Cardiac L‐type Ca2+ channel triggers transmitter release in PC 12 cells

“…Polyclonal antibodies (anti-CPZS) were generated against a 20mer peptide of the al subunit of rabbit skeletal muscle (1,419-1,431 (KHLDVVTLLRRIQPPLGFGK), coupled to bovine serum albumin by De Jongh, and used as previously described [20]). …”

β-Adrenergic regulation requires direct anchoring of PKA to cardiac Ca V 1.2 channels via a leucine zipper interaction with A kinase-anchoring protein 15

“…In cardiac muscle, a distinct ␣ 1 subunit (␣ 1 1.2a) (5,6), an ␣ 2 ␦ subunit (7), and several isoforms of ␤ subunits [␤ 1b and ␤ 2a-d (8)(9)(10)(11)] have been identified and implicated to form the Ca V 1.2 channel. As for the skeletal muscle Ca V 1.1 channel (12,13), two size forms of the ␣ 1 1.2a subunit of Ca V 1.2 channels, Ϸ240 and 210 kDa, are present in cardiac muscle and differ by truncation at the C terminus (14). Whereas the majority of Ca 2ϩ channel ␣ 1 subunits isolated from cardiac muscle are truncated (11,14,15), the cleaved distal C terminus remains associated with the truncated ␣ 1 subunit of Ca V 1.2 after proteolytic processing, and peptides derived from it can regulate channel activity (16,17).…”