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DNA Damage-binding Protein
DNA damage-binding protein or UV-DDB is a protein complex that is responsible for repair of UV-damaged DNA. This complex is composed of two protein subunits, a large subunit DDB1 (p127) and a small subunit DDB2 (p48). When cells are exposed to UV radiation, DDB1 moves from the cytosol to the nucleus and binds to DDB2, thus forming the UV-DDB complex. This complex formation is highly favorable and it is demonstrated by UV-DDB's binding preference and high affinity to the UV lesions in the DNA. This complex functions in nucleotide excision repair, recognising UV-induced (6-4) pyrimidine-pyrimidone photoproducts and cyclobutane pyrimidine dimer Pyrimidine dimers are molecular lesions formed from thymine or cytosine bases in DNA via photochemical reactions, commonly associated with direct DNA damage. Ultraviolet light (UV; particularly UVB) induces the formation of covalent linkages betwe ...s. Structure The helical domain at the n-terminus of DDB2 binds to UV damaged DNA with h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DDB1
DNA damage-binding protein 1 is a protein that in humans is encoded by the ''DDB1'' gene. Gene The gene's position is on chromosome 11q12-q13. Protein The DDB1 gene encodes the large subunit of DNA damage-binding protein, a heterodimer composed of a large and a small ( DDB2) subunit. DDB1 contains 1140 amino acids, amounting to a mass of 127 kDa. Function As its name suggests, DDB1 was initially implicated in the process of a specific type of DNA repair known as nucleotide excision repair. Since then, researchers have found that DDB1 primarily functions as a core component of the CUL4A- and CUL4B-based E3 ubiquitin ligase complexes. DDB1 serves as a bridge or adaptor protein which interacts with dozens of proteins known as DDB1 and CUL4-associated factors (DCAFs). These DCAFs are often ubiquitin ligase substrates and regulate numerous essential processes in the cell including DNA repair (DDB2), DNA replication, chromatin remodeling ( Cdt2) and more. Interactions DDB1 has be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DDB2
DNA damage-binding protein 2 is a protein that in humans is encoded by the ''DDB2'' gene. Structure As indicated by Rapić-Otrin et al. in 2003, the ''DDB2'' gene is located on human chromosome 11p11.2, spans a region of approximately 24 – 26 kb and includes 10 exons. The DDB2 protein contains five putative WD40 repeats (sequences of about 40 amino acids that can interact with each other) positioned downstream from the second exon. The WD40 motif identified in DDB2 is characteristic of proteins involved in the recognition of chromatin proteins. The C-terminal region of DDB2 (a 48 kDa molecular weight protein) is essential for binding to DDB1 (a larger 127 kDa protein). Together, the two proteins form a UV-damaged DNA binding protein complex (UV-DDB). Deficiency in humans If humans have a mutation in each copy of their ''DDB2'' gene, this causes a mild form of the human disease xeroderma pigmentosum, called XPE. Patients in the XPE group have mild dermatological manifestatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid residue ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UV Radiation
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms, it can cause chemical reactions and causes many substances to glow or fluoresce. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules. Short-wave ultraviolet light damages DNA and sterilizes surfaces with which it comes into contact. For h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleotide Excision Repair
Nucleotide excision repair is a DNA repair mechanism. DNA damage occurs constantly because of chemicals (e.g. intercalating agents), radiation and other mutagens. Three excision repair pathways exist to repair single stranded DNA damage: Nucleotide excision repair (NER), base excision repair (BER), and DNA mismatch repair (MMR). While the BER pathway can recognize specific non-bulky lesions in DNA, it can correct only damaged bases that are removed by specific glycosylases. Similarly, the MMR pathway only targets mismatched Watson-Crick base pairs. Nucleotide excision repair (NER) is a particularly important excision mechanism that removes DNA damage induced by ultraviolet light (UV). UV DNA damage results in bulky DNA adducts - these adducts are mostly thymine dimers and 6,4-photoproducts. Recognition of the damage leads to removal of a short single-stranded DNA segment that contains the lesion. The undamaged single-stranded DNA remains and DNA polymerase uses it as a templa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
