Identification of a tyrosine residue in ovine placental lactogen as essential for its binding to receptors

Gisela D. Cymes, Carlota Wolfenstein-Todel

Research output: Contribution to journalArticlepeer-review


Nitration of ovine placental lactogen (oPL) with a 10-fold molar excess of tetranitromethane over protein content resulted in the modification of 0.8 tyrosine residue. No conformational changes were observed by either fourth-derivative spectral analysis or circular dichroism. Nitration significantly decreased the binding capacity of the hormone to lactogenic and somatogenic rat liver receptors. This binding capacity was not restored by reduction of the nitro groups, thus indicating that the decrease was not due to the difference in pK between tyrosine and nitrotyrosine. The nitrotyrosine-containing peptide was isolated from a tryptic digest by HPLC and its modification extent was of 67%, which is consistent with the decrease in binding capacities (65% and 70%). Its amino acid sequence was determined and the modified tyrosine residue was identified as Tyr-46. These results provide the first evidence of the involvement of a tyrosine residue in the binding of oPL to both lactogenic and somatogenic receptors. This tyrosine appears to be a shared binding epitope between oPL and the prolactins.

Original languageEnglish (US)
Pages (from-to)31-36
Number of pages6
JournalBiochimica et Biophysica Acta - Protein Structure and Molecular Enzymology
Issue number1
StatePublished - May 2 1996
Externally publishedYes


  • Lactogenic receptor
  • Nitration
  • Ovine
  • Placental lactogen
  • Somatogenic receptor
  • Tyrosine residue

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology


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