Prolactin receptor (PRLR) is a membrane anchored protein mediating the biological actions of prolactin. The turkey PRLR (tPRLR) cDNA was isolated and characterized. The open reading frame (ORF) of tPRLR predicted 831 amino acid residues composed of a signal peptide, an extracellular domain (ECD), a single transmembrane domain and an intracellular domain. The deduced amino acid sequence of the turkey prolactin receptor is 53.8%, 51.7%, 49.8%, 49.8%, 80.3% and 89.91% identical to that of the rabbit bovine, human, long form of the rat, pigeon and chicken PRLRs, respectively. The extracellular domain contains two homologous repeat units with 63% amino acid sequence identity to each other. The membrane-distal and membrane-proximal repeats were 53--60% and 62--70% identical to the ECDs of the mammalian PRLRs, respectively. A tPRLR transcript with a molecular size of 3 kilo nucleotides was identified and was detectable in 26 tissues examined. The pituitary gland, crop sac, duodenum and gizzard were found to express the highest levels of tPRLR mRNA among the 26 tissues. In most tissues examined there was no obvious relationship between blood levels of PRL, reproductive states and estimated concentrations of the receptor mRNA. However, in the hypothalamus, increasing blood levels of PRL were associated with decreasing levels of receptor transcripts (p < 0.05), whereas, the opposite relationship was observed in the pituitary gland (p < 0.05). The extracellular domain of tPRLR (tPRLR-ECD) was expressed as a GST fusion protein (tPRLR-ECD-GST) in E. coli. The expression of tPRLR-ECD-GST in BL21 strain yielded a protein with a molecular mass of 76 kDa. About 99% of the fusion protein was present in inclusion bodies and about 50% of the total protein in inclusion bodies was the fusion protein. The insoluble fusion protein was denatured, refolded and purified using GST affinity chromatography. The yield of the purified fusion protein was 20 mg per liter with an estimated p

Zadworny, David (Supervisor)