Acetylcholine Receptor Gamma Subunit Research Articles

Nucleotide and deduced amino acid sequences of Torpedo californica acetylcholine receptor gamma subunit.

The nucleotide sequence has been determined of a cDNA clone that codes for the 60,000-dalton gamma subunit of Torpedo californica acetylcholine receptor. The length of the cDNA clone is 2,010 base pairs. The 5' and 3' untranslated regions have respective lengths of 31 and 461 base pairs. Data suggest that the putative polyadenylylation consensus sequence A-A-T-A-A-A may not be required for polyadenylylation of the mRNA corresponding to the cDNA clone described in this study. From the DNA sequence data, the amino acid sequence of the gamma subunit was deduced. The subunit is composed of 489 amino acids giving a molecular mass of 56,600 daltons. The deduced amino acid sequence data also indicate the presence of a 17-amino acid extension or signal peptide on this subunit. From these data, structural predictions for the gamma subunit are made such as potential membrane-spanning regions, possible asparagine-linked glycosylation sites, and the assignment of regions of the protein to the extracellular, internal, and cytoplasmic domains of the lipid bilayer.

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

From the electric organ of Torpedo californica, we purified mRNA that, when translated in vitro, produces polypeptides immunoprecipitable by antibodies against purified acetylcholine receptor. A novel cloning system [Okayama, H. & Berg, P. (1982) Mol. Cell. Biol. 2, 161-170] was used to produce a cDNA library from this mRNA. This library contained clones with receptor sequences identified by differential hybridization and hybridization-selection. We describe a clone of 2,030 base pairs with sequences appropriate for the amino-terminal amino acids of the gamma subunit of acetylcholine receptor. 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 2,100-base RNA present in electric organ but not in the brain of T. californica.