![]() ![]() The DNA-binding sites, response elements, consist of two half-sites, each of six base pairs. We distinguish two main types: binding of homodimers to inverted repeats, such as the steroid-hormone receptors, and binding of homo- or heterodimers (with RXR) to direct-repeat sites, such as the thyroid-hormone receptor, the retinoic-acid receptor, the vitamin D3 receptor, and peroxisome proliferation-activating receptor ( Figure 8-8). Even in the absence of antigen stimulation, a human can probably make more than 10 12 different antibody moleculesits preimmune antibody repertoire. All half-sites are separated by a number of base pairs. 2 Ligands may include other proteins (resulting in a protein-protein interaction ), 3 enzyme substrates, 4. 1 The binding partner of the macromolecule is often referred to as a ligand. Because the DNA sequence of the direct repeat is similar for all nuclear receptors concerned, a measure of discrimination is provided by varying the spacer length.įor the two inverted-repeat sequences the spacer number is always three (termed IR3), whereas for the direct repeats the number of spacers varies from 1 to 5 (termed DR1–DR5). In biochemistry and molecular biology, a binding site is a region on a macromolecule such as a protein that binds to another molecule with specificity. Each additional base pair separates the half-sites by 3.4 Å and introduces a relative rotation of 36°. The thyroid hormone-receptor homodimer (THR–THR) or heterodimer (RXR–THR) recognizes DR4. An example of a repertoire in our sense is the set of resources, institutions, and expertise that have come to define research work in contemporary systems biology, which include mathematical skills, knowledge of molecular biology, centers and funding dedicated to systems biology, and a social commitment to openness in research, expressed, for. ![]() The RXR–PPAR dimer preferably recognizes DR1, the RXR–RAR recognizes DR2 or DR5, and the dimer RXR–VDR preferably recognizes DR3. Note that the DBD of RXR is always situated upstream (5′) of its partner. Further specificity may come from binding of the modulating region to upstream or downstream DNA sequences (return to Figure 8-6(b)). It is noteworthy that nuclear-receptor binding sites are found in typical promoter regions, upstream and nearby the transcription start site, but a significant number are located in intragenic regions at distances above 25,000 base pairs (25 kb). Vincent Laudet, Hinrich Gronemeyer, in The Nuclear Receptor FactsBook, 2002 DNA binding Extensive chromosome folding will be required in order to exert an influence on transcription. ![]()
0 Comments
Leave a Reply. |