Isolation and characterization of a cDNA clone for the complete protein coding region of the delta-subunit of the mouse acetylcholine receptor

A mouse cDNA clone has been isolated that contains the complete coding region of a protein highly homologous to the δ subunit of the Torpedo acetylcholine receptor (AcChoR). The cDNA library was constructed in the vector λgt10 from membrane-associated poly(A)+ RNA from BC3H-1 mouse cells. Surprisingly, the δ clone was selected by hybridization with cDNA encoding the γ subunit of the Torpedo AcChoR. The nucleotide sequence of the mouse cDNA clone contains an open reading frame of 520 amino acids. This amino acid sequence exhibits 59% and 50% sequence homology to the Torpedo AcChoR δ and γ subunits, respectively. However, the mouse nucleotide sequence has several stretches of high homology with the Torpedo γ subunit cDNA, but not with δ. The mouse protein has the same general structural features as do the Torpedo subunits. It is encoded by a 3.3-kilobase mRNA. There is probably only one, but at most two, chromosomal genes coding for this or closely related sequences