α-Bungarotoxin-ferritin conjugates were used to visualize by freeze-fracture and thin-section electron microscopy toxin-binding sites, presumably acetylcholine (ACh) receptors, in membranes of muscle cells grown in tissue culture. Toxin conjugated to ferritin by a glutaraldehyde reaction and purified by column chromatography in a buffer of high ionic strength remains active in blocking the effect of iontophoretically applied ACh. The potency of the conjugates was decreased 5-10 times compared to native α-bungarotoxin. Toxin-ferritin conjugates were identified in small clusters which were not uniformly distributed over the surface membrane. Binding was inhibited by preincubation in D-tubocurare or unconjugated toxin. The relation of the clusters to the non-uniform distribution of ACh sensitivity and α-bungarotoxin binding on cultured muscle fibres is discussed.
Acetylcholine Receptors of Cultured Muscle Cells Demonstrated with Ferritin-α-Bungarotoxin Conjugates
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B. T. HOURANI, B. F. TORAIN, M. P. HENKART, R. L. CARTER, V. T. MARCHESI, G. D. FISCHBACH; Acetylcholine Receptors of Cultured Muscle Cells Demonstrated with Ferritin-α-Bungarotoxin Conjugates. J Cell Sci 1 November 1974; 16 (2): 473–479. doi: https://doi.org/10.1242/jcs.16.2.473
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