Identification and sequence analysis of a second form of prolactin receptor by molecular cloning of complementary DNA from rabbit mammary gland.

Two lambda gt11 clones containing fragments of cDNA encoding the prolactin receptor from rabbit mammary gland were isolated using a rat liver prolactin receptor cDNA probe. An 1848-base-pair open reading frame encodes a mature prolactin-binding protein of 592 amino acids that contains three domains: (i) the extracellular, amino-terminal, prolactin-binding region of 210 residues; (ii) the transmembrane region of 24 residues; and (iii) the intracellular, carboxyl-terminal domain of 358 residues. This latter domain is much longer than the cytoplasmic domain (57 residues) previously described for the rat liver prolactin receptor. In addition, the sequence identity of this form of prolactin receptor with the growth hormone receptor is extended in the cytoplasmic domain.