Double antenna structure of chicken prolactin receptor deduced from the cDNA sequence

Chicken prolactin receptor (cPRLR) deciphered from the cDNA sequence showed a unique double antenna structure in its extracellular domain. The predicted cPRLR preprotein was composed of 831 amino acids and contained a signal peptide and a transmembrane region. The extracellular domain comprised 438 residues, and was divided into two tandemly repeated, highly homologous units, each of which corresponded to the extracellular domains of mammalian prolactin receptors. Both extracellular units of cPRLR possessed two structural features characteristic of the ligand binding units of cytokine/prolactin receptor family, namely two pairs of cysteine residues and a WSXWS motif. These findings strongly suggest that cPRLR contains two repeated ligand binding units, that is a double antenna structure. The cPRLR gene is expressed in a wide range of tissues of laying hen.