title: Episodic evolution of prolactin receptor gene in mammals: coevolution with its ligand.
abstract: Divergence of proteins in signaling pathways requires ligand and receptor coevolution to maintain or improve binding affinity and/or specificity. In this paper we show a clear case of coevolution between the prolactin (PRL) gene and its receptor (prolactin receptor, PRLR) in mammals. First we observed episodic evolution of the extracellular and intracellular domains of the PRLR, which is closely consistent with that seen in PRL. Correlated evolution was demonstrated both between PRL and its receptor and between the two domains of the PRLR using Pearson's correlation coefficient. On comparing the ratio of the nonsynonymous substitution rate to synonymous substitution rate (omega = d(N)/d(S)) for each branch of the star phylogeny of mammalian PRLRs, separately for the extracellular domain (ECD) and the transmembrane domain/intracellular domain (TMD/ICD), we observed a lower omega ratio for ECD than TMD/ICD along those branches leading to pig, dog and rabbit but a higher ratio for ECD than TMD/ICD on the branches leading to primates, rodents and ruminants, on which bursts of rapid evolution were observed. These observations can be best explained by coevolution between PRL and its receptor and between the two domains of the PRLR.
authors.affiliation: Laboratory of Cellular and Molecular Evolution, and Molecular Biology of Domestic Animals, Kunming Institute of Zoology, Chinese Academy of Sciences, People's Republic of China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Michael
authors.initials: M
authors.lastname: Wallis
authors.forename: Ya-ping
authors.initials: YP
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019143:Evolution, Molecular; D006801:Humans; D008024:Ligands; D008322:Mammals / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011388:Prolactin / Q000235:genetics*; D011981:Receptors, Prolactin / Q000235:genetics*; D012641:Selection, Genetic; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
chemical_list: D008024:Ligands; D011981:Receptors, Prolactin; D011388:Prolactin