Gantz et al. (1997) used low-stringency PCR to isolate a fragment of a novel putative G protein-coupled receptor from human colon cancer cell line RNA. They cloned the corresponding genomic DNA from a human phage library and reported that the gene encodes a 331-amino acid polypeptide.
This gene had 7 putative transmembrane domains but less than 34% amino acid similarity to other known G protein-coupled receptors. Using Northern blotting, Gantz et al. (1997) showed that the GPR18
transcript was most abundant in human testis and spleen; transcripts were also detected in several other tissues associated with the immune system.Gantz et al. (1997) stated that the human GPR18 gene is probably intronless.