Tissue-specific expression of calcium channels.
The high-voltage-activated calcium channel is a multimeric protein complex containing α(1), α(2)/δ, β, and γ subunits. The α(1) subunit is the ion conduction channel and contains the binding sites for calcium channel blockers and toxins. Three genes code for distinct L-type, dihydropyridine-sensitive α(1) subunits; one gene codes for the neuronal P-type (Purkinje) α(1) subunit; and one gene codes for the neuronal N-type α(1) subunit. The smooth and cardiac muscle L-type calcium channel α(1) subunits are splice variants of the same gene. The α(1) subunits are coexpressed with a common α(2)/δ subunit and tissue-specific β subunits (at least three genes). The γ subunit apparently is expressed only in skeletal muscle. The properties of these cloned and expressed calcium channels are discussed here.
Institut für Pharmakologie und Toxikologie der Technischen Universität München, Biedersteiner Str. 29, 8000 München 40, Germany.
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Hullin
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Biel
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Flockerzi
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Hofmann