Molecular cloning of cDNA coding for the gamma subunit of Torpedo acetylcholine receptor.

Abstract

MRNA was purified from the electric organ of T. californica. When this mRNA was translated in vitro polypeptides immunoprecipitable by antibodies against purified acetylcholine receptor were produced. A novel cloning system (Okayama, H. and Berg, P. 1982) was used to produce a c[complementary]DNA library from this mRNA. This library contained clones with receptor sequences identified by differential hybridization and hybridization-selection. A clone of 2030 base pairs with sequences appropriate for the amino-terminal amino acids of the .gamma. subunit of acetylcholine receptor is described. This clone contains 82 bases 5'' of the codon for the amino-terminal amino acid of the mature protein. A portion of this sequence codes for a methionine followed by a 16-amino-acid polypeptide that is contiguous to the amino-terminal amino acid of the mature protein and that has the characteristics of a leader peptide. The cDNA insert hybridizes to a 2100-base RNA present in electric organ but not in the brain of T. californica.