Molecular structure of the mouse CCK-A receptor gene.

We have cloned the mouse CCK-A receptor gene (Cckar), determined its nucleotide sequence, and analyzed its expression. The receptor protein is encoded in five exons distributed over 9 kb of genomic DNA. Intron/exon borders were determined by comparing the genomic nucleotide sequence with the mouse cDNA sequence obtained by reverse transcriptase polymerase chain reaction. RNase protection analysis of Cckar transcripts revealed the presence of a splice acceptor site 200 bp upstream of the translational start codon, indicating that the promoter is associated with a non-translated exon at an upstream site. The second coding exon contains a rarely used alternative splice site that would result in the production of a truncated, 48 amino acid protein. Cckar is widely expressed in the gastrointestinal system (pancreas, gallbladder, intestine, colon and stomach), as well as in brain and kidney.