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J. Biol. Chem., Vol. 265, Issue 3, 1537-1544, Jan, 1990
KE McLane, F Tang and BM Conti-Tronconi
To identify the sequence segments of the alpha 3 subunit of the neuronal
nicotinic acetylcholine receptor (N-nAChR) forming the binding site for the
cholinergic antagonist kappa-bungarotoxin (kappa-BGT), overlapping peptides
corresponding to the complete alpha 3 sequence were tested for their
ability to bind 125I-labeled kappa-BGT. Two peptides located within the
N-terminal extracellular domain specifically bound kappa-BGT in a solid
phase assay, i.e. peptide N alpha(3)51-70 with a Kd approximately 300 nM
and peptide N alpha(3)1-18 with slightly lower affinity (Kd approximately
500 nM). Preincubation of 125I-kappa-BGT with peptides N alpha(3)51-70 or N
alpha(3)1-18 resulted in greater than 90% inhibition of kappa-125I-BGT
binding to native N-nAChR expressed on the neuronal cell line PC12. Under
the same conditions, two additional peptides, N alpha(3)180-199 and N
alpha(3)183-201, were found to inhibit kappa-125I-BGT binding to PC12 by
approximately 50%. These latter peptides represent sequences that are
homologous to those shown previously to bind alpha-bungarotoxin. Peptide N
alpha(3)51-70 (400 microM) also reduced by approximately 4- fold the
observed rate of association of kappa-BGT to PC12 cells. The results of
these experiments identify sequence segments of the alpha 3 subunit which
are likely to interact with kappa-BGT and may indicate the relative
contribution that these segments make in the formation of the high affinity
kappa-BGT-binding site of this N-nAChR subtype.
Localization of sequence segments forming a kappa-bungarotoxin-binding site on the alpha 3 neuronal nicotinic receptor
Department of Biochemistry, College of Biological Sciences, University of Minnesota, Saint Paul 55108.
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