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Stigmatellin
Stigmatellin is a potent inhibitor of the quinol oxidation (Qo) site of the cytochrome bc1 complex in mitochondria and the cytochrome b6f complex of thylakoid membranes. At higher concentrations, stigmatellin also inhibits Complex I, as a "Class B" inhibitor of that enzyme. Stigmatellin is isolated from the myxobacterium '' Stigmatella aurantica'', and contains a 5,7-dimethoxy-8-hydroxychromone aromatic headgroup with a hydrophobic alkenyl chain in position 2. Crystal structures for stigmatellin-inhibited bc1 complex from bovine, avian, yeast ('' Saccharomyces cerevisiae'') and bacterial ('' Rhodobacter capsulatus'', '' Cereibacter sphaeroides'', and ''Paracoccus denitrificans'') sources are available. Stigmatellin binds at the cytochrome b Qo site in the '(heme) bl distal' position, and associates with the Rieske iron-sulfur protein via a hydrogen bond In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) ato ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stigmatella Aurantica
''Stigmatella aurantiaca'' is a member of myxobacteria, a group of gram-negative bacteria with a complex developmental life cycle. Classification The bacterial nature of this organism was recognized by Thaxter in 1892, who grouped it among the ''Chrondromyces''. It had been described several times before, but had been misclassified as a member of the '' fungi imperfecti''. More recent investigations have shown that, contrary to Thaxter's classification, this organism is not closely related to ''Chrondromyces'', and ''Stigmatella'' is currently recognized as a separate genus. Of the three major subgroups of the myxobacteria, Myxococcus, Nannocystis, and Chrondromyces, ''Stigmatella'' is most closely aligned with Myxococcus. Life cycle ''S. aurantiaca'', like other myxobacterial species, has a complex life cycle including social gliding (swarming), fruiting body formation, and predatory feeding behaviors. The bacteria do not swim, but glide on surfaces leaving slime tra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme Inhibitor
An enzyme inhibitor is a molecule that binds to an enzyme and blocks its activity. Enzymes are proteins that speed up chemical reactions necessary for life, in which substrate molecules are converted into products. An enzyme facilitates a specific chemical reaction by binding the substrate to its active site, a specialized area on the enzyme that accelerates the most difficult step of the reaction. An enzyme inhibitor stops ("inhibits") this process, either by binding to the enzyme's active site (thus preventing the substrate itself from binding) or by binding to another site on the enzyme such that the enzyme's catalysis of the reaction is blocked. Enzyme inhibitors may bind reversibly or irreversibly. Irreversible inhibitors form a chemical bond with the enzyme such that the enzyme is inhibited until the chemical bond is broken. By contrast, reversible inhibitors bind non-covalently and may spontaneously leave the enzyme, allowing the enzyme to resume its function. Reve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhodobacter Capsulatus
''Rhodobacter capsulatus'' is a species of purple bacteria, a group of bacteria that can obtain energy through photosynthesis. Its name is derived from the Latin adjective "capsulatus" ("with a chest", "encapsulated"), itself derived Latin noun "capsula" (meaning "a small box or chest"), and the associated Latin suffix for masculine nouns, "-atus" (denoting that something is "provided with" something else). Its complete genome has been sequenced and is available to the public. Discovery The discovery of ''Rhodobacter capsulatus'' is attributed to Hans Molisch, a Czech-Austrian botanist. The microorganism, then named ''Rhodonostoc capsulatum'', was identified in 1907 in his book ''Die Purpurbakterien nach neuen Untersuchungen''. C. B. van Niel then characterized the species further in 1944 where it was renamed ''Rhodopseudomonas capsulata''. Van Niel initially described 16 strains of ''R. capsulata'' that he was able to culture from mud samples collected in California and Cuba. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rieske Protein
Rieske proteins are iron–sulfur protein (ISP) components of cytochrome ''bc''1 complexes and cytochrome b6f complexes and are responsible for electron transfer in some biological systems. John S. Rieske and co-workers first discovered the protein and in 1964 isolated an acetylated form of the bovine mitochondrial protein. In 1979 Trumpower's lab isolated the "oxidation factor" from bovine mitochondria and showed it was a reconstitutively-active form of the Rieske iron-sulfur protein It is a unique Fe-2Scluster in that one of the two Fe atoms is coordinated by two histidine residues rather than two cysteine residues. They have since been found in plants, animals, and bacteria with widely ranging electron reduction potentials from -150 to +400 mV. Biological function Ubiquinol-cytochrome-c reductase (also known as bc1 complex or complex III) is an enzyme complex of bacterial and mitochondrial oxidative phosphorylation systems. It catalyses the oxidation-reduction reaction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Histidine
Histidine (symbol His or H) is an essential amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated –NH3+ form under biological conditions), a carboxylic acid group (which is in the deprotonated –COO− form under biological conditions), and an imidazole side chain (which is partially protonated), classifying it as a positively charged amino acid at physiological pH. Initially thought essential only for infants, it has now been shown in longer-term studies to be essential for adults also. It is encoded by the codons CAU and CAC. Histidine was first isolated by Albrecht Kossel and Sven Gustaf Hedin in 1896. It is also a precursor to histamine, a vital inflammatory agent in immune responses. The acyl radical is histidyl. Properties of the imidazole side chain The conjugate acid (protonated form) of the imidazole side chain in histidine has a p''K''a of approximately 6.0. Thus, below a pH of 6, the imidazole ring ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Bond
In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a lone pair of electrons—the hydrogen bond acceptor (Ac). Such an interacting system is generally denoted , where the solid line denotes a polar covalent bond, and the dotted or dashed line indicates the hydrogen bond. The most frequent donor and acceptor atoms are the second-row elements nitrogen (N), oxygen (O), and fluorine (F). Hydrogen bonds can be intermolecular (occurring between separate molecules) or intramolecular (occurring among parts of the same molecule). The energy of a hydrogen bond depends on the geometry, the environment, and the nature of the specific donor and acceptor atoms and can vary between 1 and 40 kcal/mol. This makes them somewhat stronger than a van der Waals interaction, and weaker than fully covalent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron-sulfur Protein
Iron–sulfur proteins (or iron–sulphur proteins in British spelling) are proteins characterized by the presence of iron–sulfur clusters containing sulfide-linked di-, tri-, and tetrairon centers in variable oxidation states. Iron–sulfur clusters are found in a variety of metalloproteins, such as the ferredoxins, as well as NADH dehydrogenase, hydrogenases, coenzyme Q – cytochrome c reductase, succinate – coenzyme Q reductase and nitrogenase. Iron–sulfur clusters are best known for their role in the oxidation-reduction reactions of electron transport in mitochondria and chloroplasts. Both Complex I and Complex II of oxidative phosphorylation have multiple Fe–S clusters. They have many other functions including catalysis as illustrated by aconitase, generation of radicals as illustrated by SAM-dependent enzymes, and as sulfur donors in the biosynthesis of lipoic acid and biotin. Additionally, some Fe–S proteins regulate gene expression. Fe–S proteins are vulnerabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytochrome B
Cytochrome b within both molecular and cell biology, is a protein found in the mitochondria of eukaryotic cells. It functions as part of the electron transport chain and is the main subunit of transmembrane cytochrome bc1 and b6f complexes. Function In the mitochondrion of eukaryotes and in aerobic prokaryotes, cytochrome b is a component of respiratory chain complex III () — also known as the bc1 complex or ubiquinol-cytochrome c reductase. In plant chloroplasts and cyanobacteria, there is an analogous protein, cytochrome b6, a component of the plastoquinone-plastocyanin reductase (), also known as the b6f complex. These complexes are involved in electron transport, the pumping of protons to create a proton-motive force ( PMF). This proton gradient is used for the generation of ATP. These complexes play a vital role in cells. Structure Cytochrome b/b6 is an integral membrane protein of approximately 400 amino acid residues that probably has 8 transmembrane segments. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paracoccus Denitrificans
''Paracoccus denitrificans'', is a coccoid bacterium known for its nitrate reducing properties, its ability to replicate under conditions of hypergravity and for being a relative of the eukaryotic mitochondrion (endosymbiotic theory). Description ''Paracoccus denitrificans'', is a gram-negative, coccus, non-motile, denitrifying (nitrate-reducing) bacterium. It is typically a rod-shaped bacterium but assumes spherical shapes during the stationary phase. Like all gram-negative bacteria, it has a double membrane with a cell wall. Formerly known as ''Micrococcus denitrificans'', it was first isolated in 1910 by Martinus Beijerinck, a Dutch microbiologist. The bacterium was reclassified in 1969 to ''Paracoccus denitrificans'' by D.H. Davis. The genome of ''P. denitrificans'' was sequenced in 2004. Ecology and ecological applications Metabolically ''Paracoccus denitrificans'' is very flexible and has been recorded in soil in both aerobic or anaerobic environments. The microbe also ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhodobacter Sphaeroides
''Rhodobacter sphaeroides'' is a kind of purple bacterium; a group of bacteria that can obtain energy through photosynthesis. Its best growth conditions are anaerobic phototrophy (photoheterotrophic and photoautotrophic) and aerobic chemoheterotrophy in the absence of light. ''R. sphaeroides'' is also able to fix nitrogen.De Universiteit van Texas over ''Rhodobacter sphaeroides'' It is remarkably metabolically diverse, as it is able to grow ically via fermentation and |
Saccharomyces Cerevisiae
''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been originally isolated from the skin of grapes. It is one of the most intensively studied eukaryotic model organisms in molecular biology, molecular and cell biology, much like ''Escherichia coli'' as the model bacteria, bacterium. It is the microorganism behind the most common type of fermentation (biochemistry), fermentation. ''S. cerevisiae'' cells are round to ovoid, 5–10 micrometre, μm in diameter. It reproduces by budding. Many proteins important in human biology were first discovered by studying their Homology (biology), homologs in yeast; these proteins include cell cycle proteins, signaling proteins, and protein-processing enzymes. ''S. cerevisiae'' is currently the only yeast cell known to have Berkeley body, Berkeley bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytochrome Bc1
Cytochromes are redox-active proteins containing a heme, with a central Fe atom at its core, as a cofactor. They are involved in electron transport chain and redox catalysis. They are classified according to the type of heme and its mode of binding. Four varieties are recognized by the International Union of Biochemistry and Molecular Biology (IUBMB), cytochromes a, cytochromes b, cytochromes c and cytochrome d. Cytochrome function is linked to the reversible redox change from ferrous (Fe(II)) to the ferric (Fe(III)) oxidation state of the iron found in the heme core. In addition to the classification by the IUBMB into four cytochrome classes, several additional classifications such as cytochrome o and cytochrome P450 can be found in biochemical literature. History Cytochromes were initially described in 1884 by Charles Alexander MacMunn as respiratory pigments (myohematin or histohematin). In the 1920s, Keilin rediscovered these respiratory pigments and named them the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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