Molecular aspects of human brain sodium channel.
The sodium channel content of human brain was measured by tritiated tetrodotoxin specific binding. After solubilization, the sodium channel was submitted to chromatography on diethylaminoethyl(cellulose) Sephadex, hydroxylapatite and wheat germ agglutinin sepharose. An increase of tritiated tetrodotoxin binding specific activity was subsequently observed. Eluted sodium channels from wheat germ agglutinin sepharose were overlaid on a sucrose gradient. Electrophoretical analysis of the material obtained after the sedimentation step revealed two co-purified peptides, alpha (Mr = 275,000 mol. wt) and beta (Mr = 30,000-36,000 mol. wt.). Alpha showed an exceptionally high free electrophoretic mobility, which is a common feature for all sodium channels previously described. However, the high denaturation rate of the solubilized tetrodotoxin receptor site 1 did not allow tetrodotoxin receptor quantification by the tritiated toxin binding in sucrose fractions. Sodium channel effective reconstitution in liposomes was demonstrated: (1) 22Na+ influx in proteoliposomes was sensitive to sodium channel-specific neurotoxins: (2) reconstituted proteins showed a cation selectivity similar to that previously described for animal sodium channels. The sodium channel preparation obtained after four chromatographic steps shows two peptides on the electrophoretic analysis. Reconstituted sodium channels displayed some physiological properties found in intact conducting membranes.
De Rycker
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Laboratoire de Biochimie Générale et Comparée, Université de Liège, Belgium.
Schoffeniels
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D001921:Brain / Q000378:metabolism*; D002845:Chromatography; D004586:Electrophoresis; D006801:Humans; D007477:Ions; D008081:Liposomes / Q000378:metabolism; D008970:Molecular Weight; D009479:Neuropeptides / Q000378:metabolism; D009498:Neurotoxins / Q000494:pharmacology; D010539:Permeability; D011510:Proteolipids / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000737:chemistry / Q000378:metabolism*
D007477:Ions; D008081:Liposomes; D009479:Neuropeptides; D009498:Neurotoxins; D011510:Proteolipids; D015222:Sodium Channels; C020485:proteoliposomes; D012964:Sodium