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Selenoprotein
In molecular biology a selenoprotein is any protein that includes a selenocysteine (Sec, U, Se-Cys) amino acid residue. Among functionally characterized selenoproteins are five glutathione peroxidases (GPX) and three thioredoxin reductases, (TrxR/TXNRD) which both contain only one Sec. Selenoprotein P is the most common selenoprotein found in the plasma. It is unusual because in humans it contains 10 Sec residues, which are split into two domains, a longer N-terminal domain that contains 1 Sec, and a shorter C-terminal domain that contains 9 Sec. The longer N-terminal domain is likely an enzymatic domain, and the shorter C-terminal domain is likely a means of safely transporting the very reactive selenium atom throughout the body. Species distribution Selenoproteins exist in all major domains of life, eukaryotes, bacteria and archaea. Among eukaryotes, selenoproteins appear to be common in animals, but rare or absent in other phyla -one has been identified in the green alga '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenocysteine
Selenocysteine (symbol Sec or U, in older publications also as Se-Cys) is the 21st proteinogenic amino acid. Selenoproteins contain selenocysteine residues. Selenocysteine is an analogue of the more common cysteine with selenium in place of the sulfur. Selenocysteine is present in several enzymes (for example glutathione peroxidases, tetraiodothyronine 5′ deiodinases, thioredoxin reductases, formate dehydrogenases, glycine reductases, selenophosphate synthetase 2, methionine-''R''-sulfoxide reductase B1 ( SEPX1), and some hydrogenases). It occurs in all three domains of life, including important enzymes (listed above) present in humans. Selenocysteine was discovered by biochemist Thressa Stadtman at the National Institutes of Health. Chemistry Selenocysteine is the Se-analogue of cysteine. It is rarely encountered outside of living tissue (and is not available commercially) because it is very susceptible to air-oxidation. More common is the oxidized derivative selenocys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenium Poisoning
Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic. It seldom occurs in its elemental state or as pure ore compounds in the Earth's crust. Selenium – from Greek ( 'Moon') – was discovered in 1817 by , who noted the similarity of the new element to the previously discovered tellurium (named for the Earth). Selenium is found in metal sulfide ores, where it partially replaces the sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores, most often during production. Minerals that are pure selenide or selenate compounds are known but rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells. Applications in electronics, once important, have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenium
Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic. It seldom occurs in its elemental state or as pure ore compounds in the Earth's crust. Selenium – from Greek ( 'Moon') – was discovered in 1817 by , who noted the similarity of the new element to the previously discovered tellurium (named for the Earth). Selenium is found in metal sulfide ores, where it partially replaces the sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores, most often during production. Minerals that are pure selenide or selenate compounds are known but rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells. Applications in electronics, once important, have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GPX4
Glutathione peroxidase 4, also known as GPX4, is an enzyme that in humans is encoded by the ''GPX4'' gene. GPX4 is a phospholipid hydroperoxidase that protects cells against membrane lipid peroxidation. Function The antioxidant enzyme glutathione peroxidase 4 (GPX4) belongs to the family of glutathione peroxidases, which consists of 8 known mammalian isoenzymes (GPX1–8). GPX4 catalyzes the reduction of hydrogen peroxide, organic hydroperoxides, and lipid peroxides at the expense of reduced glutathione and functions in the protection of cells against oxidative stress. The oxidized form of glutathione (glutathione disulfide), which is generated during the reduction of hydroperoxides by GPX4, is recycled by glutathione reductase and NADPH/H+. GPX4 differs from the other GPX family members in terms of its monomeric structure, a less restricted dependence on glutathione as reducing substrate, and the ability to reduce lipid-hydroperoxides inside biological membranes. Inactivatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenoprotein P
In molecular biology, the protein domain selenoprotein P (SelP) is the only known eukaryotic selenoprotein that contains multiple selenocysteine (Sec) residues. It is a secreted glycoprotein, often found in the plasma. Its precise function remains to be elucidated; however, it is thought to have antioxidant properties. This particular protein contains two domains: the C terminal and N terminal domain. The N-terminal domain is larger than the C terminal and the N-terminal is thought to be glycosylated. Function SelP may have antioxidant properties. It can attach to epithelial cells, and may protect vascular endothelial cells against peroxynitrite toxicity. The high selenium content of SelP suggests that it may be involved in selenium intercellular transport or storage. The promoter structure of bovine SelP suggests that it may be involved in countering heavy metal intoxication, and may also have a developmental function. Structure The N-terminal region always contains one Sec r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cysteine
Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, sometimes the symbol Cyz is used. The deprotonated form can generally be described by the symbol Cym as well. The thiol is susceptible to oxidation to give the disulfide derivative cystine, which serves an important structural role in many proteins. In this case, the symbol Cyx is sometimes used. When used as a food additive, it has the E number E920. Cysteine is encoded by the codons UGU and UGC. The sulfur-containing amino acids cysteine and methionine are more easily oxidized than the other amino acids. Structure Like other amino acids (not as a residue of a protein), cysteine exists as a zwitterion. Cysteine has chirality in the older / notation based on homology to - and -glyceraldehyde. In the newer ''R''/''S'' system of design ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iodothyronine Deiodinase
Iodothyronine deiodinases ( and ) are a subfamily of deiodinase enzymes important in the activation and deactivation of thyroid hormones. Thyroxine (T4), the precursor of 3,5,3'-triiodothyronine (T3) is transformed into T3 by deiodinase activity. T3, through binding a nuclear thyroid hormone receptor, influences the expression of genes in practically every vertebrate cell. Iodothyronine deiodinases are unusual in that these enzymes contain selenium, in the form of an otherwise rare amino acid selenocysteine. These enzymes are not to be confused with the iodotyrosine deiodinases that are also deiodinases, but not members of the iodothyronine family. The iodotyrosine deiodinases (unlike the iodothyronine deiodinases) do ''not'' use selenocysteine or selenium. The iodotyrosine enzymes work on iodinated single tyrosine residue molecules to scavenge iodine, and do not use as substrates the double-tyrosine residue molecules of the various iodo thyronines. Activation and inactivat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glutathione Peroxidase
Glutathione peroxidase (GPx) () is the general name of an enzyme family with peroxidase activity whose main biological role is to protect the organism from oxidative damage. The biochemical function of glutathione peroxidase is to reduce lipid hydroperoxides to their corresponding alcohols and to reduce free hydrogen peroxide to water. Isozymes Several isozymes are encoded by different genes, which vary in cellular location and substrate specificity. Glutathione peroxidase 1 (GPx1) is the most abundant version, found in the cytoplasm of nearly all mammalian tissues, whose preferred substrate is hydrogen peroxide. Glutathione peroxidase 4 (GPx4) has a high preference for lipid hydroperoxides; it is expressed in nearly every mammalian cell, though at much lower levels. Glutathione peroxidase 2 is an intestinal and extracellular enzyme, while glutathione peroxidase 3 is extracellular, especially abundant in plasma. So far, eight different isoforms of glutathione peroxidase (G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eubacterium Barkeri
''Eubacterium barkeri'', previously known as ''Clostridium barkeri'', is a bacterium belonging to the Bacillota The Bacillota (synonym Firmicutes) are a phylum of bacteria, most of which have gram-positive cell wall structure. The renaming of phyla such as Firmicutes in 2021 remains controversial among microbiologists, many of whom continue to use the earl .... References External linksType strain of ''Eubacterium barkeri'' at Bac''Dive'' - the Bacterial Diversity Metadatabase Eubacteriaceae Bacteria described in 1972 {{clostridia-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell (biology)
The cell is the basic structural and functional unit of life forms. Every cell consists of a cytoplasm enclosed within a membrane, and contains many biomolecules such as proteins, DNA and RNA, as well as many small molecules of nutrients and metabolites.Cell Movements and the Shaping of the Vertebrate Body in Chapter 21 of Molecular Biology of the Cell '' fourth edition, edited by Bruce Alberts (2002) published by Garland Science. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos. It is also common to describe small molecules such as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multi-wavelength Anomalous Dispersion
Multi-wavelength anomalous diffraction (sometimes Multi-wavelength anomalous dispersion; abbreviated MAD) is a technique used in X-ray crystallography that facilitates the determination of the three-dimensional structure of biological macromolecules (e.g. DNA, drug receptors) via solution of the phase problem. MAD was developed by Wayne Hendrickson while working as a postdoctoral researcher under Jerome Karle at the United States Naval Research Laboratory. The mathematics upon which MAD (and progenitor Single wavelength anomalous dispersion) were based were developed by Jerome Karle, work for which he was awarded the 1985 Nobel Prize in Chemistry (along with Herbert Hauptman). See also * Single wavelength anomalous dispersion Single-wavelength anomalous diffraction (SAD) is a technique used in X-ray crystallography that facilitates the determination of the structure of proteins or other biological macromolecules by allowing the solution of the phase problem. In contrast ... (S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
