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Purification of the Saxitoxin Receptor of the Sodium Channel from Rat Brain
Robert P. Hartshorne and William A. Catterall
Proceedings of the National Academy of Sciences of the United States of America
Vol. 78, No. 7, [Part 2: Biological Sciences] (Jul., 1981), pp. 4620-4624
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/10668
Page Count: 5
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The saxitoxin (STX) receptor has been purified 740-fold from rat brain by a combination of ion exchange chromatography, wheat germ agglutinin chromatography, and sedimentation on sucrose gradients to a specific activity of 1488 pmol/mg of protein. The best fractions were estimated to be 47% pure from their specific activity or 66% pure on the basis of NaDodSO4 gel electrophoresis. Two polypeptides, α (Mr≈ 270,000± 10,000) and β (Mr≈ 38,300± 2000) (mean ± SD) copurify with STX binding activity. Two polypeptides of the same apparent Mr are specifically covalently labeled by photoreactive derivatives of 125I-labeled scorpion toxin in rat brain synaptosomes and are likely to be identical to α and β . The solubilized STX receptor has a Mr of 316,000± 63,000, limiting its composition to one α polypeptide and one or more β polypeptides per soluble receptor. Our results suggest that the α and β polypeptides contain both the STX binding site and the scorpion toxin binding site of the mammalian sodium channel.
Proceedings of the National Academy of Sciences of the United States of America © 1981 National Academy of Sciences