The progesterone receptor is an intracellular steroid receptor that specifically binds progesterone. Expressed by a single gene (chromosome 11q22), it has two main forms, A and B, that differ in their molecular weight.

Structure

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Like all steroid receptors, the progesterone receptor has an amino acid and a carboxyl terminal, and between them the regulatory domain, a DNA binding domain, the hinge section, and the hormone binding domain. A special transcription activation function (TAF), called TAF-3, is present in the progesterone receptor-B, in a B-upstream segment (BUS) at the amino acid terminal. This segment is not present in the receptor-A.

Function

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Estrogen is necessary to induce the progesterone receptors. When no binding hormone is present the carboxyl terminal inhibits transcription. Binding to a hormone induces a structural change that removes the inhibitory action. Progesterone antagonists prevent the structural reconfiguration.

After progesterone binds to the receptor, restructuring with dimerization follows and the complex enters the nucleus and binds to DNA. There transcription takes place, resulting in formation of messenger RNA that activates cytoplasmatic ribosomes to produce specific proteins.

See also

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• Selective progesterone receptor modulator

Reference

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Speroff L, Glass RH, Kase NG: Clinical Gynecologic Endocrinology and Infertility. Sixth Ed. Lippincott Williams & Wilkins, Baltimore,MD, 1999.

External links

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Intracellular receptors