Neuropeptide Y, peptide YY, and pancreatic polypeptide are homologous 36-amino acid peptides that differ from most other peptide transmitters by having a relatively rigid conformation in aqueous solutions, defined as the pancreatic polypeptide fold, and a critical C-terminal tyrosine amide. These peptides serve as gastrointestinal hormones and neurotransmitters. A cDNA encoding a novel G protein-coupled receptor activated by neuropeptide Y was cloned from Drosophila by use of degenerate oligonucleotide primers and polymerase chain reaction amplification of cDNA prepared from transcripts expressed early in embryogenesis. The cDNA encodes a protein of 449 amino acids with the characteristics of a G protein-coupled receptor and shares significant amino acid identity with mammalian tachykinin receptors. When expressed in Xenopus oocytes, the PR4 protein is activated by mammalian neuropeptides in the order: peptide YY greater than neuropeptide Y much greater than pancreatic polypeptide. Northern analysis showed that PR4 receptor is expressed at equivalent levels in adult Drosophila head and body and that the expression of the PR4 receptor is regulated during development. The molecular characterization of this receptor should lead to a better understanding of the functional role of this important family of hormone receptors in adult organisms and during development.