MOLECULAR-CLONING OF A NEW MEMBER OF THE PUTATIVE G-PROTEIN-COUPLED RECEPTOR GENE FROM BARNACLE BALANUS AMPHITRITE

An intronless gene encoding a putative G protein-coupled receptor was isolated from the genomic library of barnacle Balanus amphitrite Darwi n, with probes obtained from degenerate polymerase chain reaction (PCR ) primers used to amplify putative transmembrane regions. The cloned g enome DNA specifies an open reading frame of 1431 bp encoding 476 amin o acids with seven hydrophobic transmembrane (TM)-spanning regions. Th e predicted protein contains potential asparagine-linked glycosylation and serine/threonine phosphorylation sites in the N-terminal and intr acellular loops, respectively. Moreover, the protein has a consensus G protein-binding motif (Ala-Ile-Ser-Leu-Asp-Arg-Tyr-Leu-Ala) in TM dom ain III. This receptor is most closely related to human alpha(2)-adren ergic receptor with 36.9% identity in 409 amino acids overlap. It is a lso homologous to human serotonin(1A) (5HT), snail pond 5HT and mouse D-2-dopamine receptors with 33-36% identities. Within TM regions among these biogenic amine receptors, the cloned receptor shows considerabl e amino acid homology with more than 40% overall identities.