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L-arabinose Operon
The L-arabinose operon, also called the ''ara'' or ''araBAD'' operon, is an operon required for the breakdown of the five-carbon sugar L-arabinose in ''Escherichia coli''. The L-arabinose operon contains three structural genes: ''araB'', ''araA'', ''araD'' (collectively known as ''araBAD''), which encode for three metabolic enzymes that are required for the metabolism of L-arabinose. AraB ( ribulokinase), AraA (an isomerase), AraD (an epimerase) produced by these genes catalyse conversion of L-arabinose to an intermediate of the pentose phosphate pathway, D-xylulose-5-phosphate. The structural genes of the L-arabinose operon are transcribed from a common promoter into a single transcript, a mRNA. The expression of the L-arabinose operon is controlled as a single unit by the product of regulatory gene ''araC'' and the catabolite activator protein (CAP)-cAMP complex. The regulator protein AraC is sensitive to the level of arabinose and plays a dual role as both an activator in ... [...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 repressor, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operon
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 since the discovery of the first operons in eukaryotes in the early 1990s, more evidence has arisen to suggest they are more common than previously assumed. In general, expression of prokaryotic operons leads to the generation of polycistronic mRNAs, while eukaryotic operons lead to monocistronic mRNA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regulatory Gene
A regulator gene, regulator, or regulatory gene is a gene involved in controlling the expression of one or more other genes. Regulatory sequences, which encode regulatory genes, are often at the five prime end (5') to the start site of transcription of the gene they regulate. In addition, these sequences can also be found at the three prime end (3') to the transcription start site. In both cases, whether the regulatory sequence occurs before (5') or after (3') the gene it regulates, the sequence is often many kilobases away from the transcription start site. A regulator gene may encode a protein, or it may work at the level of RNA, as in the case of genes encoding microRNAs. An example of a regulator gene is a gene that codes for a repressor protein that inhibits the activity of an operator (a gene which binds repressor proteins thus inhibiting the translation of RNA to protein via RNA polymerase). In prokaryotes, regulator genes often code for repressor proteins. Repressor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regulatory Protein
Regulation of gene expression, or gene regulation, includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA). Sophisticated programs of gene expression are widely observed in biology, for example to trigger developmental pathways, respond to environmental stimuli, or adapt to new food sources. Virtually any step of gene expression can be modulated, from Transcriptional regulation, transcriptional initiation, to RNA processing, and to the post-translational modification of a protein. Often, one gene regulator controls another, and so on, in a gene regulatory network. Gene regulation is essential for viruses, prokaryotes and eukaryotes as it increases the versatility and adaptability of an organism by allowing the cell to express protein when needed. Although as early as 1951, Barbara McClintock showed interaction between two genetic loci, Activator (''Ac'') and Dissociator (''Ds''), in the color f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structure Of L-arabinose Operon Of E
A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as biological organisms, minerals and chemicals. Abstract structures include data structures in computer science and musical form. Types of structure include a hierarchy (a cascade of one-to-many relationships), a network featuring many-to-many links, or a lattice featuring connections between components that are neighbors in space. Load-bearing Buildings, aircraft, skeletons, anthills, beaver dams, bridges and salt domes are all examples of load-bearing structures. The results of construction are divided into buildings and non-building structures, and make up the infrastructure of a human society. Built structures are broadly divided by their varying design approaches and standards, into categories including building structures, archi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proceedings Of The National Academy Of Sciences Of The United States Of America
''Proceedings of the National Academy of Sciences of the United States of America'' (often abbreviated ''PNAS'' or ''PNAS USA'') is a peer-reviewed multidisciplinary scientific journal. It is the official journal of the National Academy of Sciences, published since 1915, and publishes original research, scientific reviews, commentaries, and letters. According to ''Journal Citation Reports'', the journal has a 2021 impact factor of 12.779. ''PNAS'' is the second most cited scientific journal, with more than 1.9 million cumulative citations from 2008 to 2018. In the mass media, ''PNAS'' has been described variously as "prestigious", "sedate", "renowned" and "high impact". ''PNAS'' is a delayed open access journal, with an embargo period of six months that can be bypassed for an author fee ( hybrid open access). Since September 2017, open access articles are published under a Creative Commons license. Since January 2019, ''PNAS'' has been online-only, although print issues are ava ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight, where it is used to make cellulose in cell walls, the most abundant carbohydrate in the world. In energy metabolism, glucose is the most important source of energy in all organisms. Glucose for metabolism is stored as a polymer, in plants mainly as starch and amylopectin, and in animals as glycogen. Glucose circulates in the blood of animals as blood sugar. The naturally occurring form of glucose is -glucose, while -glucose is produced synthetically in comparatively small amounts and is less biologically active. Glucose is a monosaccharide containing six carbon atoms and an aldehyde group, and is therefore an aldohexose. The glucose molecule can exist in an open-chain (acyclic) as well as ring (cyclic) form. Gluco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. ''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 on an agar plate containing only glucose and lactose, the bacteria will use glucose first and lactose second. Wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catabolism
Catabolism () is the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions. Catabolism breaks down large molecules (such as polysaccharides, lipids, nucleic acids, and proteins) into smaller units (such as monosaccharides, fatty acids, nucleotides, and amino acids, respectively). Catabolism is the breaking-down aspect of metabolism, whereas anabolism is the building-up aspect. Cells use the monomers released from breaking down polymers to either construct new polymer molecules or degrade the monomers further to simple waste products, releasing energy. Cellular wastes include lactic acid, acetic acid, carbon dioxide, ammonia, and urea. The formation of these wastes is usually an oxidation process involving a release of chemical free energy, some of which is lost as heat, but the rest of which is used to drive the synthesis of adenosine triphosphate (ATP). This molecule acts as a way f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of Molecular Biology
The ''Journal of Molecular Biology'' is a biweekly peer-reviewed scientific journal covering all aspects of molecular biology. It was established in 1959 and is published by Elsevier. The editor-in-chief is Peter Wright ( The Scripps Research Institute). Abstracting and indexing The journal is abstracted and indexed in: According to the ''Journal Citation Reports'', the journal has a 2020 impact factor of 5.469. Notable articles Some of the most highly cited articles that have appeared in the journal are: *, in which Jacques Monod, Jeffries Wyman, and Jean-Pierre Changeux presented the MWC model, that explained the cooperativity exhibited by allosteric proteins, such as hemoglobin. *, in which Edwin Southern presented the first description of nucleic acid blotting, a technique that revolutionized the field of molecular biology. *, in which the Smith–Waterman algorithm for determining the degree of homology of DNA, RNA, or protein sequences was first described. *, in which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BioEssays
''BioEssays'' is a monthly peer-reviewed review journal covering molecular and cellular biology. Areas covered include genetics, genomics, epigenetics, evolution, developmental biology, neuroscience, human biology, physiology, systems biology, and plant biology. The journal also publishes commentaries on aspects of science communication, education, policy, and current affairs. History The journal was established in December 1984 by founding editor-in-chief William J. Whelan under the auspices of the International Union of Biochemistry and Molecular Biology. Adam S. Wilkins became editor in January 1990. Originally published by ICSU Press and The Company of Biologists, ''BioEssays'' has been published by John Wiley & Sons since January 1998. Andrew Moore became editor-in-chief in August 2008. Kerstin Brachhold is current editor-in-chief. Post-publication commenting ''BioEssays'' offers an article-commenting facility via its website. Topics of particular current attention are of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Activator (genetics)
A transcriptional activator is a protein (transcription factor) that increases transcription of a gene or set of genes. Activators are considered to have ''positive'' control over gene expression, as they function to promote gene transcription and, in some cases, are required for the transcription of genes to occur. Most activators are DNA-binding proteins that bind to enhancers or promoter-proximal elements. The DNA site bound by the activator is referred to as an "activator-binding site". The part of the activator that makes protein–protein interactions with the general transcription machinery is referred to as an "activating region" or "activation domain". Most activators function by binding sequence-specifically to a regulatory DNA site located near a promoter and making protein–protein interactions with the general transcription machinery (RNA polymerase and general transcription factors), thereby facilitating the binding of the general transcription machinery to the prom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
