Purification, cloning, and tissue distribution of a 23-kDa rat protein isolated by morphine affinity chromatography

Mol Endocrinol. 1990 Sep;4(9):1370-6. doi: 10.1210/mend-4-9-1370.


A 23-kDa (p23k) rat brain protein was stereospecifically eluted from a 14 beta-bromoacetamidomorphine affinity column, purified to apparent homogeneity by reverse phase HPLC, and partially sequenced. Three degenerate oligodeoxynucleotide probes were synthesized based on this partial amino acid sequence. A rat brain cDNA library was screened using these probes, and a full-length cDNA was isolated. The deduced protein, 187 amino acids long, is rich in glutamic and aspartic acid residues, endowing p23k with a net negative charge at neutral pH. The protein lacks a signal sequence as well as any transmembrane domains. Based on predictions of secondary structure, p23k is a globular protein composed of 30% alpha-helices and 18% beta-pleated sheets. Northern blot analysis revealed p23k transcripts in rat brain, liver, and the mouse x rat neuroblastoma-glioma NG108-14 cell line. Although not an opioid receptor itself, this protein may be associated with such a receptor or be related to a protein that has been shown to be cross-linked to the opioid peptide beta-endorphin.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Aspartic Acid / analysis
  • Base Sequence
  • Brain Chemistry
  • Chromatography, Affinity*
  • Chromatography, High Pressure Liquid
  • Cloning, Molecular
  • DNA / isolation & purification
  • Glutamates / analysis
  • Glutamic Acid
  • Hydrogen-Ion Concentration
  • Liver / chemistry
  • Male
  • Molecular Sequence Data
  • Molecular Weight
  • Morphine Derivatives*
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / isolation & purification*
  • Oligonucleotide Probes
  • Protein Conformation
  • Rats
  • Rats, Inbred Strains
  • Tissue Distribution
  • Tumor Cells, Cultured


  • Glutamates
  • Morphine Derivatives
  • Nerve Tissue Proteins
  • Oligonucleotide Probes
  • Aspartic Acid
  • Glutamic Acid
  • 14 beta-bromoacetamidomorphine
  • DNA