DNA binding domain (DBD) | |||||||||
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Crystallographic structure of the human progesterone receptor DNA-binding domain dimer (cyan and green) complexed with double stranded DNA (magenta). Zinc atoms of are depicted as grey spheres.
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Identifiers | |||||||||
Symbol | zf-C4 | ||||||||
Pfam | PF00105 | ||||||||
InterPro | IPR001628 | ||||||||
SMART | SM00399 | ||||||||
PROSITE | PDOC00031 | ||||||||
SCOP | 1hra | ||||||||
SUPERFAMILY | 1hra | ||||||||
CDD | cd06916 | ||||||||
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Available protein structures: | |
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Pfam | structures |
PDB | RCSB PDB; PDBe; PDBj |
PDBsum | structure summary |
Ligand-binding domain (LBD) | |||||||||
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Crystallographic structure of the ligand binding domain of the human RORγ (rainbow colored, N-terminus = blue, C-terminus = red) complexed with 25-hydroxycholesterol (space-filling model (carbon = white, oxygen = red) and the NCOA2 coactivator (magneta).
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Identifiers | |||||||||
Symbol | Hormone_recep | ||||||||
Pfam | PF00104 | ||||||||
InterPro | IPR000536 | ||||||||
SMART | SM00430 | ||||||||
SCOP | 1lbd | ||||||||
SUPERFAMILY | 1lbd | ||||||||
CDD | cd06157 | ||||||||
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Available protein structures: | |
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Pfam | structures |
PDB | RCSB PDB; PDBe; PDBj |
PDBsum | structure summary |
In the field of molecular biology, nuclear receptors are a class of proteins found within cells that are responsible for sensing steroid and thyroid hormones and certain other molecules. In response, these receptors work with other proteins to regulate the expression of specific genes, thereby controlling the development, homeostasis, and metabolism of the organism.
Nuclear receptors have the ability to directly bind to DNA and regulate the expression of adjacent genes, hence these receptors are classified as transcription factors. The regulation of gene expression by nuclear receptors generally only happens when a ligand — a molecule that affects the receptor's behavior — is present. More specifically, ligand binding to a nuclear receptor results in a conformational change in the receptor, which, in turn, activates the receptor, resulting in up- or down-regulation of gene expression.
A unique property of nuclear receptors that differentiates them from other classes of receptors is their ability to directly interact with and control the expression of genomic DNA. As a consequence, nuclear receptors play key roles in both embryonic development and adult homeostasis. As discussed below, nuclear receptors may be classified according to either mechanism or homology.
Nuclear receptors are specific to metazoans (animals) and are not found in protists, algae, fungi, or plants. Amongst the early-branching animal lineages with sequenced genomes, two have been reported from the sponge Amphimedon queenslandica, two from the ctenophore Mnemiopsis leidyi four from the placozoan Trichoplax adhaerens and 17 from the cnidarian Nematostella vectensis. There are 270 nuclear receptors in the nematode C. elegans alone. Humans, mice, and rats have respectively 48, 49, and 47 nuclear receptors each.