We report the isolation and sequence of a cDNA clone that encodes a locust (Schistocerca gregaria) nervous system nicotinic acetylcholine receptor (AChR) subunit (aLl). The calculated molecular weight of the unglycosylated polypeptide, which contains in the proposed extracellular domain two adjacent cysteine residues which are characteristic of a (ligand binding) subunits, is 60 641 daltons. Injection into Xenopus oocytes, of RNA synthesized from this clone in vitro, results in expression of functional nicotinic receptors in the oocyte membrane. In these, nicotine opens a cation channel; the receptors are blocked by both a-bungarotoxin (a-Bgt) and x-bungarotoxin (x-Bgt). Reversible block of the expressed insect AChR by mecamylamine, d-tubocurarine, tetraethylammonium, bicuculline and strychnine has also been observed. These data are entirely consistent with previously reported electrophysiological studies on in vivo insect nicotinic receptors and also with biochemical studies on an cx-Bgt affinity purified locust AChR. Thus, a functional receptor exhibiting the characteristic pharmacology of an in vivo insect nicotiniic AChR can be expressed in Xenopus oocytes by injection with a single subunit RNA.

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