Structure and Expression of the Human Motilin Gene

The human motilin gene was isolated from a human genomic library and its structure was determined by restriction mapping and DNA sequence analysis. The gene consists of five exons separated by four introns spanning approximately 9 kb of genomic DNA. Exon I encodes the 5′ untranslated portion of the motilin mRNA. Exons II and III encode the signal peptide and the 22-amino-acid motilin peptide; codons encoding the motilin moiety are split by an intron. The carboxy-terminal motilin-associated peptide (MAP) is largely encoded by Exons III and IV with the last two amino acids of the motilin precursor and the 3′ untranslated region encoded by Exon V. Thus, the motilin gene has an unusual structure in which a small bioactive peptide is encoded on two distinct exons. Examination of the expression of the human and nonhuman primate motilin gene by Northern hybridization analysis indicates that it is expressed in a number of gastrointestinal and extragastrointestinal tissues.