Cloning and tissue‐specific expression of the brain calcium channel β‐subunit

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Abstract
A cDNA clone encoding a protein with high homology to the β‐subunit of the rabbit skeletal muscle dihydropyridine‐sensitive calcium channel was isolated from a rat brain cDNA library. This rat brain β‐subunit cDNA hybridizes to a 3.4 kb message that is expressed in high levels in the cerebral hemispheres and hippocampus but is significantly reduced in cerebellum. The open reading frame encodes 597 amino acids with a predicted mass of 65 679 Da which is 82% homologous with the skeletal muscle β‐subunit. The brain cDNA encodes a unique 153 amino acid C‐terminus and predicts the absence of a muscle‐specific 50 amino acid internal segment. It also encodes numerous consensus phosphorylation sites suggesting a role in calcium channel regulation. The corresponding human β‐subunit gene was localized to chromosome 17. Hence the encoded brain β‐Subunit. which has a primary structure highly similar to its isoform in skeletal muscle, may have a comparable role as an integral regulatory component of a neuronal calcium channel.