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Locus Of Enterocyte Effacement-encoded Regulator
The locus of enterocyte effacement-encoded regulator (Ler) is a regulatory protein that controls bacterial pathogenicity of enteropathogenic ''Escherichia coli'' (EPEC) and enterohemorrhagic ''Escherichia coli'' (EHEC). More specifically, Ler regulates the locus of enterocyte effacement (LEE) pathogenicity island genes, which are responsible for creating intestinal attachment and effacing lesions and subsequent diarrhea: LEE1, LEE2, and LEE3. LEE1, 2, and 3 carry the information necessary for a type III secretion system. The transcript encoding the Ler protein is the open reading frame 1 on the LEE1 operon. The mechanism of Ler regulation involves competition with histone-like nucleoid structuring protein (H-NS), a negative regulator of the LEE pathogenicity island. Ler is regulated by many factors such as plasmid encoded regulator (Per), integration host factor, Fis, BipA, a positive regulatory loop involving GrlA, and quorum sensing mediated by ''luxS''. __TOC__ Mechanis ... [...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] |
Histone-like Nucleoid-structuring Protein
Histone-like nucleoid-structuring protein (H-NS), is one of twelve nucleoid-associated proteins (NAPs) whose main function is the organization of genetic material, including the regulation of gene expression via xenogeneic silencing. H-NS is characterized by an N-terminal domain (NTD) consisting of two dimerization sites, a linker region that is unstructured and a C-terminal domain (CTD) that is responsible for DNA-binding. Though it is a small protein (15 kDa), it provides essential nucleoid compaction and regulation of genes (mainly silencing) and is highly expressed, functioning as a dimer or multimer. Change in temperature causes H-NS to be dissociated from the DNA duplex, allowing for transcription by RNA polymerase, and in specific regions lead to pathogenic cascades in enterobacteria such as ''Escherichia coli'' and the four ''Shigella'' species. Structure H-NS has a specific topology that allows it to condense bacterial DNA into a superhelical structure based on evide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Organization
Nuclear organization refers to the spatial distribution of chromatin within a cell nucleus. There are many different levels and scales of nuclear organisation. Chromatin is a higher order structure of DNA. At the smallest scale, DNA is packaged into units called nucleosomes. The quantity and organisation of these nucleosomes can affect the accessibility of local chromatin. This has a knock-on effect on the expression of nearby genes, additionally determining whether or not they can be regulated by transcription factors. At slightly larger scales, DNA looping can physically bring together DNA elements that would otherwise be separated by large distances. These interactions allow regulatory signals to cross over large genomic distances—for example, from enhancers to promoters. In contrast, on a large scale, the arrangement of chromosomes can determine their properties. Chromosomes are organised into two compartments labelled A ("active") and B ("inactive"), each with dis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GTPase
GTPases are a large family of hydrolase enzymes that bind to the nucleotide guanosine triphosphate (GTP) and hydrolyze it to guanosine diphosphate (GDP). The GTP binding and hydrolysis takes place in the highly conserved P-loop "G domain", a protein domain common to many GTPases. Functions GTPases function as molecular switches or timers in many fundamental cellular processes. Examples of these roles include: * Signal transduction in response to activation of cell surface receptors, including transmembrane receptors such as those mediating taste, smell and vision. * Protein biosynthesis (a.k.a. translation) at the ribosome. * Regulation of cell differentiation, proliferation, division and movement. * Translocation of proteins through membranes. * Transport of vesicles within the cell, and vesicle-mediated secretion and uptake, through GTPase control of vesicle coat assembly. GTPases are active when bound to GTP and inactive when bound to GDP. In the generalized recepto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autoinducer
Autoinducers are signaling molecules that are produced in response to changes in cell-population density. As the density of quorum sensing bacterial cells increases so does the concentration of the autoinducer. Detection of signal molecules by bacteria acts as stimulation which leads to altered gene expression once the minimal threshold is reached. Quorum sensing is a phenomenon that allows both Gram-negative and Gram-positive bacteria to sense one another and to regulate a wide variety of physiological activities. Such activities include symbiosis, virulence, motility, antibiotic production, and biofilm formation. Autoinducers come in a number of different forms depending on the species, but the effect that they have is similar in many cases. Autoinducers allow bacteria to communicate both within and between different species. This communication alters gene expression and allows bacteria to mount coordinated responses to their environments, in a manner that is comparable to be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Autonomous University Of Mexico
The National Autonomous University of Mexico ( es, Universidad Nacional Autónoma de México, UNAM) is a public research university in Mexico. It is consistently ranked as one of the best universities in Latin America, where it's also the biggest in terms of enrollment. A portion of UNAM's main campus in Mexico City, known as '' Ciudad Universitaria'' (University City), is a UNESCO World Heritage site that was designed by some of Mexico's best-known architects of the 20th century and hosted the 1968 Summer Olympic Games. Murals in the main campus were painted by some of the most recognized artists in Mexican history, such as Diego Rivera and David Alfaro Siqueiros. With acceptance rates usually below 10%, and its research, especially in Artificial Intelligence, being recognized by UNESCO as one of the most impactful globally, UNAM is known for its high quality research and educational level. All Mexican Nobel laureates are either alumni or faculty of UNAM. UNAM was founded, in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
S-ribosylhomocysteine Lyase
The enzyme S-ribosylhomocysteine lyase (EC 4.4.1.21) catalyzes the reaction :''S''-(5-deoxy-D-ribos-5-yl)-L-homocysteine = L-homocysteine + (4''S'')-4,5-dihydroxypentan-2,3-dione Nomenclature This enzyme belongs to the family of lyases, specifically the class of carbon-sulfur lyases. The systematic name of this enzyme class is ''S''-(5-deoxy-D-ribos-5-yl)-L-homocysteine L-homocysteine-lyase 4''S'')-4,5-dihydroxypentan-2,3-dione-forming''. Other names in common use include ''S''-ribosylhomocysteinase, and LuxS. This enzyme participates in methionine metabolism. Structure and function LuxS is a homodimeric iron-dependent metalloenzyme containing two identical tetrahedral metal-binding sites similar to those found in peptidases and amidases. Furthermore, LuxS is involved in the synthesis of autoinducer AI-2 (autoinducer-2), which mediates quorum sensing in roughly half of bacterial species. AI-2, a furanosyl borate diester, is a small signaling molecule generated by bacter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quorum Sensing
In biology, quorum sensing or quorum signalling (QS) is the ability to detect and respond to cell population density by gene regulation. As one example, QS enables bacteria to restrict the expression of specific genes to the high cell densities at which the resulting phenotypes will be most beneficial. Many species of bacteria use quorum sensing to coordinate gene expression according to the density of their local population. In a similar fashion, some social insects use quorum sensing to determine where to nest. Quorum sensing in pathogenic bacteria activates host immune signaling and prolongs host survival, by limiting the bacterial intake of nutrients, such as tryptophan, which further is converted to serotonin. As such, quorum sensing allows a Commensalism, commensal interaction between host and pathogenic bacteria. Quorum sensing may also be useful for cancer cell communications. In addition to its function in biological systems, quorum sensing has several useful applications ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lambda Phage
''Enterobacteria phage λ'' (lambda phage, coliphage λ, officially ''Escherichia virus Lambda'') is a bacterial virus, or bacteriophage, that infects the bacterial species ''Escherichia coli'' (''E. coli''). It was discovered by Esther Lederberg in 1950. The wild type of this virus has a temperate life cycle that allows it to either reside within the genome of its host through lysogeny or enter into a lytic phase, during which it kills and lyses the cell to produce offspring. Lambda strains, mutated at specific sites, are unable to lysogenize cells; instead, they grow and enter the lytic cycle after superinfecting an already lysogenized cell. The phage particle consists of a head (also known as a capsid), a tail, and tail fibers (see image of virus below). The head contains the phage's double-strand linear DNA genome. During infection, the phage particle recognizes and binds to its host, ''E. coli'', causing DNA in the head of the phage to be ejected through the tail into the ... [...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] |
Bacterium
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of 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 soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of 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, such as hydrogen sulphide and methane, to energy. Bacteria also live in symbiotic and parasitic relationshi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open Reading Frame
In molecular biology, open reading frames (ORFs) are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible reading frames will be "open" (the "reading", however, refers to the RNA produced by transcription of the DNA and its subsequent interaction with the ribosome in translation). Such an ORF may contain a start codon (usually AUG in terms of RNA) and by definition cannot extend beyond a stop codon (usually UAA, UAG or UGA in RNA). That start codon (not necessarily the first) indicates where translation may start. The transcription termination site is located after the ORF, beyond the translation stop codon. If transcription were to cease before the stop codon, an incomplete protein would be made during translation. In eukaryotic genes with multiple exons, introns are removed and exons are then joined together after transcription to yield the final ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
