The affinity labeling of partially purified acetylcholine receptor from electric tissue of Electrophorus

A. Karlin, David Cowburn

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Abstract

The receptor for acetylcholine was partially purified by affinity chromatography of an extract in Triton X 100 of membrane fragments from electric tissue. The receptor was assayed, after its reduction with dithiothreitol, by reaction with the affinity alkylating agent, [methyl 3H]4 (N maleimido) benzyl trimethyl ammonium iodide. Alternative labeling procedures, one useful for routine assay of picomole quantities of receptor and the other for labeling larger quantities of receptor, are described. The purified receptor specifically incorporated about 3 nmol of label per mg of protein. This incorporation was blocked by pretreatment of the receptor with Naja naja siamensis neurotoxin. The rate of the affinity reaction was similar to that found with membrane fragments and with intact electroplax. Furthermore, as in intact electroplax [3H]4 (N maleimido) benzyl trimethyl ammonium iodide reacted 5000 fold faster with the reduced receptor than did [14C]N ethylmaleimide. When purified receptor was labeled with [3H]4 (N maleimido) benzyl trimethyl ammonium iodide and subjected to electrophoresis on polyacrylamide gels in dodecyl sulfate and dithiothreitol, three major protein bands were observed. Only one of these, however, contained 3H activity; its mobility indicating a molecular weight of 40,000.

Original languageEnglish (US)
JournalProceedings of the National Academy of Sciences of the United States of America
Volume70
Issue number12
StatePublished - 1973

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Electrophorus
Cholinergic Receptors
Dithiothreitol
Elapidae
Ethylmaleimide
Membranes
Alkylating Agents
Octoxynol
Neurotoxins
Affinity Chromatography
Polyacrylamide Gel Electrophoresis
Proteins
Molecular Weight
ammonium iodide

ASJC Scopus subject areas

  • General
  • Genetics

Cite this

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abstract = "The receptor for acetylcholine was partially purified by affinity chromatography of an extract in Triton X 100 of membrane fragments from electric tissue. The receptor was assayed, after its reduction with dithiothreitol, by reaction with the affinity alkylating agent, [methyl 3H]4 (N maleimido) benzyl trimethyl ammonium iodide. Alternative labeling procedures, one useful for routine assay of picomole quantities of receptor and the other for labeling larger quantities of receptor, are described. The purified receptor specifically incorporated about 3 nmol of label per mg of protein. This incorporation was blocked by pretreatment of the receptor with Naja naja siamensis neurotoxin. The rate of the affinity reaction was similar to that found with membrane fragments and with intact electroplax. Furthermore, as in intact electroplax [3H]4 (N maleimido) benzyl trimethyl ammonium iodide reacted 5000 fold faster with the reduced receptor than did [14C]N ethylmaleimide. When purified receptor was labeled with [3H]4 (N maleimido) benzyl trimethyl ammonium iodide and subjected to electrophoresis on polyacrylamide gels in dodecyl sulfate and dithiothreitol, three major protein bands were observed. Only one of these, however, contained 3H activity; its mobility indicating a molecular weight of 40,000.",
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AU - Karlin, A.

AU - Cowburn, David

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N2 - The receptor for acetylcholine was partially purified by affinity chromatography of an extract in Triton X 100 of membrane fragments from electric tissue. The receptor was assayed, after its reduction with dithiothreitol, by reaction with the affinity alkylating agent, [methyl 3H]4 (N maleimido) benzyl trimethyl ammonium iodide. Alternative labeling procedures, one useful for routine assay of picomole quantities of receptor and the other for labeling larger quantities of receptor, are described. The purified receptor specifically incorporated about 3 nmol of label per mg of protein. This incorporation was blocked by pretreatment of the receptor with Naja naja siamensis neurotoxin. The rate of the affinity reaction was similar to that found with membrane fragments and with intact electroplax. Furthermore, as in intact electroplax [3H]4 (N maleimido) benzyl trimethyl ammonium iodide reacted 5000 fold faster with the reduced receptor than did [14C]N ethylmaleimide. When purified receptor was labeled with [3H]4 (N maleimido) benzyl trimethyl ammonium iodide and subjected to electrophoresis on polyacrylamide gels in dodecyl sulfate and dithiothreitol, three major protein bands were observed. Only one of these, however, contained 3H activity; its mobility indicating a molecular weight of 40,000.

AB - The receptor for acetylcholine was partially purified by affinity chromatography of an extract in Triton X 100 of membrane fragments from electric tissue. The receptor was assayed, after its reduction with dithiothreitol, by reaction with the affinity alkylating agent, [methyl 3H]4 (N maleimido) benzyl trimethyl ammonium iodide. Alternative labeling procedures, one useful for routine assay of picomole quantities of receptor and the other for labeling larger quantities of receptor, are described. The purified receptor specifically incorporated about 3 nmol of label per mg of protein. This incorporation was blocked by pretreatment of the receptor with Naja naja siamensis neurotoxin. The rate of the affinity reaction was similar to that found with membrane fragments and with intact electroplax. Furthermore, as in intact electroplax [3H]4 (N maleimido) benzyl trimethyl ammonium iodide reacted 5000 fold faster with the reduced receptor than did [14C]N ethylmaleimide. When purified receptor was labeled with [3H]4 (N maleimido) benzyl trimethyl ammonium iodide and subjected to electrophoresis on polyacrylamide gels in dodecyl sulfate and dithiothreitol, three major protein bands were observed. Only one of these, however, contained 3H activity; its mobility indicating a molecular weight of 40,000.

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