title: The saxitoxin receptor of the sodium channel from rat brain. Evidence for two nonidentical beta subunits.
abstract: The saxitoxin receptor of the sodium channel purified from rat bran contains three types of subunits: alpha with Mr approximately 270,000, beta 1 with Mr approximately 39,000, and beta 2 with Mr approximately 37,000. These are the only polypeptides which quantitatively co-migrate with the purified saxitoxin receptor during velocity sedimentation through sucrose gradients. beta 1 and beta 2 are often poorly resolved by gel electrophoresis in sodium dodecyl sulfate (SDS), but analysis of the effect of beta-mercaptoethanol on the migration is covalently attached to the alpha subunit by disulfide bonds while the beta 1 subunit is not. The alpha and beta subunits of the sodium channel were covalently labeled in situ in synaptosomes using a photoreactive derivative of scorpion toxin. Treatment of SDS-solubilized synaptosomes with beta-mercaptoethanol decreases the apparent molecular weight of the alpha subunit band without change in the amount of 125I-labeled scorpion toxin associated with either the alpha or beta subunit bands. These results indicate that the alpha and beta 1 subunits are labeled by scorpion toxin whereas beta 1 is not and that the beta 2 subunit is covalently attached to alpha by disulfide bonds in situ as well as in purified preparations.
mesh_terms: D029845:Amphibian Proteins; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002352:Carrier Proteins / Q000302:isolation & purification* / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008623:Mercaptoethanol / Q000494:pharmacology; D008970:Molecular Weight; D051381:Rats
chemical_list: D029845:Amphibian Proteins; D002352:Carrier Proteins; D007473:Ion Channels; D046911:Macromolecular Substances; C027525:saxitoxin-binding protein, Rana catesbeiana; D008623:Mercaptoethanol