CLONING OF A MELATONIN-RELATED RECEPTOR FROM HUMAN PITUITARY

We have cloned an orphan G protein-coupled receptor from a human pitui tary cDNA library using a probe generated by PCR, The cDNA, designated H9, encodes a protein of 613 amino acids that is 45% identical at the amino acid level to the recently cloned human Mel(1a) and Mel(1b) mel atonin receptors. Structural analyses of the encoded protein and its g ene, along,vith phylogenetic analysis, further show that H9 is closely related to the G protein-coupled melatonin receptor family, Unusual f eatures of the protein encoded by H9 include a lack of N-linked glycos ylation sites and a carboxyl tail >300 amino acids long, H9 transientl y expressed in COS-1 cells did not bind [I-125]melatonin or [H-3]melat onin, H9 mRNA is expressed in hypothalamus and pituitary, suggesting t hat the encoded receptor and its natural ligand are involved in neuroe ndocrine function.