Prolactin is a pituitary hormone involved in the stimulation of milk production, salt and water regulation, growth, development and reproduction. The initial step in its action is the binding to a specific membrane receptor (prolactin receptor) which belongs to the superfamily of class 1 cytokine receptors. The function of the prolactin receptor is mediated, at least in part, by two families of signaling molecules: Janus kinases and signal transducers and activators of transcription. Prolactin (PRL) is a hormone involved in a variety of important functions including ion transport and osmoregulation, stimulation of milk, protein synthesis as well as the regulation of numerous reproductive functions. PRL exerts its influence on different cell types through a signal transduction pathway which begins with the binding of the hormone to a transmembrane PRL receptor. Immunoreactive PRL receptor, a member of the cytokine receptor family, varies in size (short and long forms) with tissue source and species, from ~40 kD to 100 kD. The PRL receptor consists of at least three separate domains: an extracellular region with 5 cysteines which contains the prolactin binding site, a single transmembrane domain and a cytoplasmic region, the length of which appears to influence ligand binding and regulate cellular function. Recombinant protein corresponding to rabbit Prolactin extracellular domain, expressed in E. coli. Amino Acid Sequence: The sequence of the first five N-terminal amino acids was determined and was found to be Gly-Lys-Pro-Phe-Ile. Biological Activity: Activity is determined by the dose-dependant inhibition of Prolactin-stimuled proliferation of Nb2 cells and by high affinity binding of oPLR and other lactogenic hormones. Protein Content: UV spectroscopy at 280 nm using the absorbency value of 2.63 as the extinction coefficient for a 0.1% (1mg/ml) solution. This value is calculated by the PC GENE computer analysis program of protein sequences (IntelliGenetics). Storage and Stability: Lyophilized and reconstituted products are stable for 6 months after receipt at -20C. Reconstitute with sterile buffer. Aliquot to avoid repeated freezing and thawing. Store at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
