Beta 2 subunits of sodium channels from vertebrate brain. Studies with subunit-specific antibodies |
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Authors: | D A Wollner D J Messner W A Catterall |
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Affiliation: | Department of Pharmacology, University of Washington School of Medicine, Seattle 98195. |
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Abstract: | The sodium channel purified from rat brain is composed of three subunits: alpha (Mr 260,000), beta 1 (Mr 36,000), and beta 2 (Mr 33,000). alpha and beta 2 subunits are linked through disulfide bonds. Procedures are described for preparative isolation of the beta 1 and beta 2 subunits under native conditions. Pure beta 2 subunits obtained by this procedure were used to prepare a specific anti-beta 2 subunit antiserum. Antibodies purified from this serum by antigen affinity chromatography recognize only disulfide-linked alpha beta 2 complexes and beta 2 subunits in immunoblots, and immunoprecipitate 32P-labeled alpha subunits of purified sodium channels having intact disulfide bonds, but not those of sodium channels from which beta 2 subunits have been detached by reduction of disulfide bonds. These antibodies also immunoprecipitate 89% of the high affinity saxitoxin-binding sites from rat brain membranes, indicating that nearly all sodium channels in rat brain have disulfide-linked alpha beta 2 subunits. Approximately 22% of beta 2 subunits in adult rat brain are not disulfide-linked to alpha subunits. Anti-beta 2 subunit antibodies are specific for sodium channels in the central nervous system and will not cross-react with sodium channels in skeletal muscle or sciatic nerve. The brains of a broad range of vertebrate species, including electric eel, are shown to express sodium channels with disulfide-linked alpha beta 2 subunits. |
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