Characterization and quantification of pyridoxal 5'-phosphate-extracted nuclear progesterone receptor

Tong J. Chen, Richard G. MacDonald, William F. Robidoux, Wendell W. Leavitt

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8 Scopus citations

Abstract

Pyridoxal phosphate extracts progesterone receptors from the nuclear fraction of hamster uterus. Optimal extraction occurs after 2 h at 2 C with 5 mM pyridoxal phosphate. At millimolar concentrations, pyridoxal phosphate also extracts non-receptor proteins from the nuclei, in amounts equivalent to those released by high salt (0.5 M KO) treatment (~10 mg protein per gram tissue). Thus, although pyridoxal phosphate is a useful probe for studying the interaction of steroid receptors with nuclear components, it does not selectively extract nuclear steroid receptors. The pyridoxal phosphate-extracted nuclear progesterone receptor had a sedimentation coefficient of 3.3S. Upon reduction with sodium borohydride, this species was converted to a 2.5S molecule. Sodium borohydride reduction of the pyridoxal phosphate-extracted nuclear receptor also caused a significant change in the steroid binding specificity of the molecule. The steroid specificity of the unreduced pyridoxal phosphate-extracted nuclear receptor was virtually identical to that of the KCl-extracted nuclear receptor. In contrast, deoxycorticosterone and 5α-pregnanedione competed 3- to 8-fold less effectively with progesterone for binding to the reduced form of pyridoxal phosphate-extracted nuclear receptor as compared to the other receptor forms.

Original languageEnglish (US)
Pages (from-to)1023-1028
Number of pages6
JournalJournal of Steroid Biochemistry
Volume14
Issue number10
DOIs
Publication statusPublished - Oct 1981

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ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology

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