Recognition of inter-transmembrane regions of acetylcholine receptor alpha subunit by antibodies, T cells and neurotoxins. Implications for membrane-subunit organization.
Three regions of the alpha chain of Torpedo californica acetylcholine receptor (AChR), corresponding to residues alpha 262-276, alpha 388, 408 and alpha 427-437 were synthesized, purified and characterized. The first two peptides have been proposed to occupy inter-transmembrane regions while the third represented the C-terminal segment, proposed by various models to be either extracellular or intracellular. Peptide alpha 388-408 stimulated a good response in the AChR-primed T cells of H-2s haplotype mice, a low response in the H-2q haplotype and no response in the H-2b haplotype. Peptide alpha 427-437 stimulated AChR-primed T cells of the H-2s haplotype, but caused no response in the q and b haplotypes. Peptide alpha 262-276 evoked no in vitro stimulation in any of the s, q or b haplotypes. In antibody binding studies, peptide alpha 388-408 bound antibodies raised against free AChR or against membrane-bound AChR. The other two peptides showed little or no binding activity. Further, peptide alpha 388-408 bound specifically both 125I-labelled bungarotoxin and cobratoxin, while the other two peptides had no binding activity. These results were consistent with only one of the models for subunit organization within the membrane.
Atassi
M Z
MZ
Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030.
Manshouri
T
T
Yokoi
T
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D000818:Animals; D000906:Antibodies / Q000276:immunology*; D002038:Bungarotoxins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D003039:Cobra Neurotoxin Proteins / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D009498:Neurotoxins / Q000378:metabolism*; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology / Q000494:pharmacology; D011950:Receptors, Cholinergic / Q000138:chemical synthesis / Q000302:isolation & purification / Q000502:physiology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000502:physiology*; D014101:Torpedo / Q000378:metabolism
D000906:Antibodies; D002038:Bungarotoxins; D003039:Cobra Neurotoxin Proteins; D009498:Neurotoxins; D010446:Peptide Fragments; D011950:Receptors, Cholinergic