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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Purification and protein sequence analysis of rat liver prolactin receptor.

Prolactin receptors were purified from rat liver membranes by single-step immunoaffinity chromatography using a specific monoclonal antibody to the rat liver prolactin receptor. Scatchard analysis of 125I-human growth hormone binding to the purified receptor revealed two classes of specific binding sites with Ka = 18.5 x 10(9) and 1.2 x 10(9) M-1. Considering that both classes of binding sites are responsible for high affinity prolactin binding, the partially purified receptor preparation had a binding activity of 1.69 nmol/mg protein, representing 1000-fold purification over microsomal receptors with a recovery of 52%. From three separate purifications, 6 mg of partially purified prolactin receptor were obtained with a purity of approximately 4 to 6.5%. Thus, the use of monoclonal antibody for affinity chromatography resulted in a large improvement of prolactin receptor purification compared to previous hormone affinity chromatography (300-fold purification, 15% recovery). The purified receptor was run on preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis, and a homogeneous preparation of prolactin receptor was obtained by electroelution from gel slices corresponding to Mr 38,000-43,000. Immunoblot analysis using a radiolabeled monoclonal antibody revealed two separate but closely located bands of Mr 42,000 and 40,000 in microsomal, partially purified, and electroeluted preparations. The homogeneous receptor protein was extensively digested with L-1-tosylamido-2-phenylethyl chloromethyl ketone trypsin, and 10 internal amino acid sequences of the rat liver prolactin receptor were determined by gas-phase sequence analysis. Oligonucleotide probes were prepared against two of these internal sequences, and a prolactin receptor cDNA was isolated from a rat liver library using one of these probes (Boutin, J. M., Jolicoeur, C., Okamura, H., Gagnon, J., Edery, M., Shirota, M., Banville, D., Dusanter-Fourt, I., Djiane, J., and Kelly, P. A. (1988) Cell 53, 69-77). The amino acid sequence deduced from the cDNA reveals three potential sites of N-linked glycosylation, two of which were confirmed during protein sequencing. The prolactin receptor was characterized by affinity labeling with 125I-human growth hormone. Cross-linking of microsomes revealed a single band for the hormone-receptor complex with Mr 62,000. On the other hand, cross-linking of Triton X-100-solubilized or partially purified receptor with labeled hormone resulted in the appearance of two bands with Mr 62,000 and 102,000, suggesting the existence of a subunit structure of the prolactin receptor, or alternatively, the existence of two types of prolactin receptor.(ABSTRACT TRUNCATED AT 400 WORDS)[1]

References

  1. Purification and protein sequence analysis of rat liver prolactin receptor. Okamura, H., Raguet, S., Bell, A., Gagnon, J., Kelly, P.A. J. Biol. Chem. (1989) [Pubmed]
 
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