Synthetic peptides used to locate the alpha-bungarotoxin binding site and immunogenic regions on alpha subunits of the nicotinic acetylcholine receptor |
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Authors: | S Ralston V Sarin H L Thanh J Rivier J L Fox J Lindstrom |
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Affiliation: | Salk Institute for Biological Studies, San Diego, California 92138. |
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Abstract: | Synthetic peptides corresponding to 57% of the sequence of alpha subunits of acetylcholine receptors from Torpedo californica electric organ and extending from the NH2 to the COOCH terminus have been synthesized. The alpha-bungarotoxin binding site on denatured alpha subunits was mapped within the sequence alpha 185-199 by assaying binding of 125I-alpha-bungarotoxin to slot blots of synthetic peptides. Further studies showed that residues in the sequence alpha 190-194, especially cysteines-alpha 192, 193, were critical for binding alpha-bungarotoxin. Reduction and alkylation studies suggested that these cysteines must be disulfide linked for alpha-bungarotoxin to bind. Binding sites for serum antibodies to native receptors or alpha subunits were mapped by indirect immunoprecipitation of 125I-peptides. Several antigenic sequences were identified, but a synthetic peptide corresponding to the main immunogenic region (which is highly conformation dependent) was not identified. |
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