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Catabolite Repression
Carbon catabolite repression, or simply catabolite repression, is an important part of global control system of various bacteria and other microorganisms. Catabolite repression allows microorganisms to adapt quickly to a preferred (rapidly metabolizable) carbon and energy source first. This is usually achieved through inhibition of synthesis of enzymes involved in catabolism of carbon sources other than the preferred one. The catabolite repression was first shown to be initiated by glucose and therefore sometimes referred to as the glucose effect. However, the term "glucose effect" is actually a misnomer since other carbon sources are known to induce catabolite repression. It was discovered by Frédéric Diénert in 1900. Jacques Monod provides a bibliography of pre-1940 literature. ''Escherichia coli'' Catabolite repression was extensively studied in ''Escherichia coli''. ''E. coli'' grows faster on glucose than on any other carbon source. For example, if ''E. coli'' is placed o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit the air, soil, water, Hot spring, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the nitrogen fixation, fixation of nitrogen from the Earth's atmosphere, atmosphere. The nutrient cycle includes the decomposition of cadaver, dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adenylyl Cyclase
Adenylate cyclase (EC 4.6.1.1, also commonly known as adenyl cyclase and adenylyl cyclase, abbreviated AC) is an enzyme with systematic name ATP diphosphate-lyase (cyclizing; 3′,5′-cyclic-AMP-forming). It catalyzes the following reaction: :ATP = 3′,5′-cyclic AMP + diphosphate It has key regulatory roles in essentially all Cell (biology), cells. It is the most Polyphyly, polyphyletic known enzyme: six distinct classes have been described, all catalysis, catalyzing the same reaction but representing unrelated gene Gene family, families with no known Sequence homology, sequence or structural homology. The best known class of adenylyl cyclases is class III or AC-III (Roman numerals are used for classes). AC-III occurs widely in eukaryotes and has important roles in many human Tissue (biology), tissues. All classes of adenylyl cyclase Catalysis, catalyse the conversion of adenosine triphosphate (ATP) to cyclic adenosine monophosphate, 3',5'-cyclic AMP (cAMP) and pyrophosphate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit the air, soil, water, Hot spring, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the nitrogen fixation, fixation of nitrogen from the Earth's atmosphere, atmosphere. The nutrient cycle includes the decomposition of cadaver, dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operons
In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo splicing to create monocistronic mRNAs that are translated separately, i.e. several strands of mRNA that each encode a single gene product. The result of this is that the genes contained in the operon are either expressed together or not at all. Several genes must be ''co-transcribed'' to define an operon. Originally, operons were thought to exist solely in prokaryotes (which includes organelles like plastids that are derived from bacteria), but their discovery in eukaryotes was shown in the early 1990s, and are considered to be rare. In general, expression of prokaryotic operons leads to the generation of polycistronic mRNAs, while eukaryotic operons lead to monocistronic mRNAs. Operons are also found in viruses such as bacteriophages. For ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CcpA
Catabolite Control Protein A (CcpA) is a master regulator of carbon metabolism in gram-positive bacteria. It is a member of the LacI/ GalR transcription regulator family. In contrast to most LacI/GalR proteins, CcpA is allosterically regulated principally by a protein-protein interaction, rather than a protein-small molecule interaction. CcpA interacts with the phosphorylated form of Hpr and Crh, which is formed when high concentrations of glucose or fructose-1,6-bisphosphate are present in the cell. Interaction of Hpr or Crh modulates the DNA sequence specificity of CcpA, allowing it to bind operator DNA to modulate transcription. Small molecules glucose-6-phosphate and fructose-1,6-bisphosphate Fructose 1,6-bisphosphate, known in older publications as Harden-Young ester, is fructose sugar phosphorylated on carbons 1 and 6 (i.e., is a fructosephosphate). The β-D-form of this compound is common in cells. Upon entering the cell, most glu ... are also known allosteric effec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacillus Subtilis
''Bacillus subtilis'' (), known also as the hay bacillus or grass bacillus, is a gram-positive, catalase-positive bacterium, found in soil and the gastrointestinal tract of ruminants, humans and marine sponges. As a member of the genus ''Bacillus'', ''B. subtilis'' is rod-shaped, and can form a tough, protective endospore, allowing it to tolerate extreme environmental conditions. ''B. subtilis'' has historically been classified as an obligate aerobe, though evidence exists that it is a facultative anaerobe. ''B. subtilis'' is considered the best studied Gram-positive bacterium and a model organism to study bacterial chromosome replication and cell differentiation. It is one of the bacterial champions in secreted enzyme production and used on an industrial scale by biotechnology companies. Description ''Bacillus subtilis'' is a Gram-positive bacterium, rod-shaped and catalase-positive. It was originally named ''Vibrio subtilis'' by Christian Gottfried Ehrenberg, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcriptional Regulation
In molecular biology and genetics, transcriptional regulation is the means by which a cell regulates the conversion of DNA to RNA ( transcription), thereby orchestrating gene activity. A single gene can be regulated in a range of ways, from altering the number of copies of RNA that are transcribed, to the temporal control of when the gene is transcribed. This control allows the cell or organism to respond to a variety of intra- and extracellular signals and thus mount a response. Some examples of this include producing the mRNA that encode enzymes to adapt to a change in a food source, producing the gene products involved in cell cycle specific activities, and producing the gene products responsible for cellular differentiation in multicellular eukaryotes, as studied in evolutionary developmental biology. The regulation of transcription is a vital process in all living organisms. It is orchestrated by transcription factors and other proteins working in concert to finely tune t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Repressor
In molecular genetics, a repressor is a DNA- or RNA-binding protein that inhibits the expression of one or more genes by binding to the operator or associated silencers. A DNA-binding repressor blocks the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes into messenger RNA. An RNA-binding repressor binds to the mRNA and prevents translation of the mRNA into protein. This blocking or reducing of expression is called repression. Function If an inducer, a molecule that initiates the gene expression, is present, then it can interact with the repressor protein and detach it from the operator. RNA polymerase then can transcribe the message (expressing the gene). A co-repressor is a molecule that can bind to the repressor and make it bind to the operator tightly, which decreases transcription. A repressor that binds with a co-repressor is termed an ''aporepressor'' or ''inactive repressor''. One type of aporepressor is the trp repre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catabolite Activator Protein
In cell biology, catabolite activator protein (CAP), which is also known as cAMP receptor protein (CRP), is a trans-acting transcriptional activator in bacteria that effectively catalyzes the initiation of DNA transcription by interacting with RNA polymerase in a way that causes the DNA to bend. CAP's name reflects the protein's ability to affect transcription of genes involved in many catabolic pathways. For example, when the amount of glucose transported into a cell is low, a cascade of events results in the increase of cAMP levels in the cell's cytosol, and this increase in cAMP levels is sensed by CAP, which goes on to activate the transcription of many other catabolic genes. CAP exists as a homodimer in solution, and it is bound to by two cyclic AMP (cAMP) ligand molecules with negative cooperativity. By increasing CAP's affinity for DNA, cyclic AMP functions as an allosteric effector. With its cyclic-AMP ligand, CAP binds a DNA region upstream from the site at whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclic Adenosine Monophosphate
Cyclic adenosine monophosphate (cAMP, cyclic AMP, or 3',5'-cyclic adenosine monophosphate) is a second messenger, or cellular signal occurring within cells, that is important in many biological processes. cAMP is a derivative of adenosine triphosphate (ATP) and used for intracellular signal transduction in many different organisms, conveying the cAMP-dependent pathway. History Earl Sutherland of Vanderbilt University won a Nobel Prize in Physiology or Medicine in 1971 "for his discoveries concerning the mechanisms of the action of hormones", especially epinephrine, via second messengers (such as cyclic adenosine monophosphate, cyclic AMP). Synthesis The synthesis of cAMP is stimulated by trophic hormones that bind to receptors on the cell surface. cAMP levels reach maximal levels within minutes and decrease gradually over an hour in cultured cells. Cyclic AMP is synthesized from ATP by adenylate cyclase located on the inner side of the plasma membrane and anchored at v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permease
The permeases are membrane transport proteins, a class of multipass transmembrane proteins that allow the diffusion of a specific molecule in or out of the cell in the direction of a concentration gradient, a form of facilitated diffusion Facilitated diffusion (also known as facilitated transport or passive-mediated transport) is the process of spontaneous passive transport (as opposed to active transport) of molecules or ions across a biological membrane via specific transmembr .... The permease binding is the first step of translocation. LacY protein from Escherichia coli is an example of a permease. See also * Lactose permease * Beta-galactoside permease It was originally discovered in the 1930s by Joy Adames . It is a transporter protein that helps in various aspects of cellular life including DNA replication, translation of RNA, and diffusion. * Amino acid permease A permease (porter) is a protein or protein complex that catalyzes a vectorial reaction, irrespective ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
