Transport of nutrients through the digestive system is highly dependent on gastrointestinal (GI) motility. GI motility disorders include gastroesophageal reflux disease, gastroparesis (diabetic and post surgical), irritable bowel syndrome, and constipation. Motilin, a 22-amino acid peptide hormone that is secreted by enterochromaffin cells of the small intestine, influences gastric motility by inducing interdigestive (phase III) antrum and duodenal contractions. Most recently, an orphan GPCR related to growth hormone secretagogues receptor (GHS-R) has been isolated and characterized from human stomach as the motilin receptor (MTLR or GPR38; 52% identity with GHS-R). The structurally unrelated macrolide antibiotic erythromycin is known to have Motilin-like side effects, including vomiting, nausea, diarrhea, and abdominal muscular discomfort. MTLR is expressed in enteric neurons of the human duodenum and colon. Interestingly, the macrolide antibiotic erythromycin also binds to MTLR, providing a molecular basis for its effects on the human GI tract.

Motilin gene (human chromosome 6p21.2) consists of 5 exons spanning approximately 9 kb of genomic DNA. Exon 1 encodes the 5-prime untranslated portion of the motilin mRNA. Exons 2 and 3 encode the signal peptide and the 22-amino acid motilin peptide. The 22-aa mature motilin peptide is highly conserved across species. The motilin prohomrone consists of 115 amino acids and includes a 25-residue N-terminal signal peptide followed by the 22-amino-acid motilin sequence and a long, 68-residue Motilin-related C-terminal peptide. Proteolytic processing of promotilin to motilin occurs at a very unusual and rare "Lys-Lys" sequence. High-affinity binding sites for motilin have been detected in the GI tract of humans and other species and in the central nervous system of rabbits.

MTLR/GPR38 (human chromosome 13q14-q21) encodes a protein with all the features of GPCR, including seven predicted TM domains. MTLR is alternatively spliced. MTLR1A/GPR38-A is 412 aa and GPR38-B is 386-aa with 5 TM domains. MTLR is 52% identical with the recently cloned and characterized GHS-R or Ghrelin receptor. MTLR gene is conserved distantly in evolution. GPR38 is ~54% identical with a related gene (75E7) in the teleost puffer fish Spheroides nephelus which evolved ~400 million years ago. Expression GPR38 was found in human enteric neurons of the human duodenum and colon, thyroid, and bone marrow.

ADI has produced antibodies to motilin, and Motilin receptor using peptide sequences specific for each protein. The appropriate control immunogenic peptides are also available to confirm specificity of antibodies. Purified motilin (full length) is available for various studies.

~CT=near C-terminus; h= Human; m= Mouse; r= Rat; b= Bovine, p=Pig, Ch=chicken, c=canine, rb=rabbit, mo=monkey

"Neat Antisera" are the unpurified antiserum and it is suitable for ELISA and Western.
"Affinity pure" IgG may be more suitable for immunohistochemical applications and to reduce background in most applications.
"Control peptides" cannot be used for Western as they are very short peptides. They are intended for ELISA or antibody blocking studies to establish antibody specificity.