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TisB-IstR Toxin-antitoxin System
The TisB-IstR toxin-antitoxin system is the first known toxin-antitoxin system which is induced by the SOS response in response to DNA damage. IstR-1 and IstR-2 IstR sRNA (inhibitor of SOS-induced toxicity by RNA) is a family of non-coding RNA first identified in ''Escherichia coli''. There are two small RNAs encoded by the IstR locus: IstR-1 and IstR-2, of which IstR-1 works as antitoxins against the toxic proteinbr>TisB(toxicity-induced by SOS B) which is encoded by the neighbouring ''tisAB'' gene. IstR-1 is a 75 nucleotide transcript expressed constitutively throughout growth, whereas IstR-2 is a 140 nucleotide transcript induced by Mitomycin C (MMC). Both IstR-2 and ''tisAB'' are thought to be regulated by LexA while IstR-1 is constitutively transcribed. Deletion analysis confirmed the function of IstR, ''E. coli'' strain K-12 could not grow in the absence of IstR when ''tisAB'' was present. Inserting IstR genes on a plasmid allowed the bacteria to grow normally. Further stud ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enterobacteriaceae
Enterobacteriaceae is a large family (biology), family of Gram-negative bacteria. It was first proposed by Rahn in 1936, and now includes over 30 genera and more than 100 species. Its classification above the level of family is still a subject of debate, but one classification places it in the order Enterobacterales of the class Gammaproteobacteria in the phylum Pseudomonadota. In 2016, the description and members of this family were emended based on comparative genomic analyses by Adeolu et al. Enterobacteriaceae includes, along with many harmless Symbiosis, symbionts, many of the more familiar pathogenic bacteria, pathogens, such as ''Salmonella'', ''Escherichia coli'', ''Klebsiella'', and ''Shigella''. Other disease-causing bacteria in this family include ''Enterobacter'' and ''Citrobacter''. Members of the Enterobacteriaceae can be Bacterial taxonomy#Nomenclature, trivially referred to as enterobacteria or "enteric bacteria",as several members live in the intestines of anim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. These products are often proteins, but in non-protein-coding genes such as transfer RNA (tRNA) and small nuclear RNA (snRNA), the product is a functional non-coding RNA. Gene expression is summarized in the central dogma of molecular biology first formulated by Francis Crick in 1958, further developed in his 1970 article, and expanded by the subsequent discoveries of reverse transcription and RNA replication. The process of gene expression is used by all known life—eukaryotes (including multicellular organisms), prokaryotes (bacteria and archaea), and utilized by viruses—to generate the macromolecular machinery for life. In genetics, gene expression is the most fundamental level at which the genotype gives rise to the phenotype, '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antisense RNA
Antisense RNA (asRNA), also referred to as antisense transcript, natural antisense transcript (NAT) or antisense oligonucleotide, is a single stranded RNA that is complementary to a protein coding messenger RNA (mRNA) with which it hybridizes, and thereby blocks its translation into protein. asRNAs (which occur naturally) have been found in both prokaryotes and eukaryotes, and can be classified into short (200 nucleotides) non-coding RNAs (ncRNAs). The primary function of asRNA is regulating gene expression. asRNAs may also be produced synthetically and have found wide spread use as research tools for gene knockdown. They may also have therapeutic applications. Discovery and history in drug development Some of the earliest asRNAs were discovered while investigating functional proteins. An example was micF asRNA. While characterizing the outer membrane porin in ''E.coli'', some of the promoter clones observed were capable of repressing the expression of other membrane porin s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hok/sok System
The hok/sok system is a postsegregational killing mechanism employed by the R1 plasmid in ''Escherichia coli''. It was the first type I toxin-antitoxin pair to be identified through characterisation of a plasmid-stabilising locus. It is a type I system because the toxin is neutralised by a complementary RNA, rather than a partnered protein (type II toxin-antitoxin). Genes involved The hok/sok system involves three genes: * ''hok'', host killing - a long lived (half-life 20 minutes) toxin * ''sok'', suppression of killing - a short lived (half-life 30 seconds) RNA antitoxin * ''mok'', modulation of killing - required for ''hok'' translation Killing mechanism When ''E. coli'' undergoes cell division, the two daughter cells inherit the long-lived hok toxin from the parent cell. Due to the short half-life of the sok antitoxin, daughter cells inherit only small amounts and it quickly degrades. If a daughter cell has inherited the R1 plasmid, it has inherited the ''sok'' gene and a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sib RNA
Sib RNA refers to a group of related non-coding RNA. They were originally named QUAD RNA after they were discovered as four repeat elements in ''Escherichia coli'' intergenic regions. The family was later renamed Sib (for short intergenic abundant sequences) when it was discovered that the number of repeats is variable in other species and in other ''E. coli'' strains. Identification These small RNA were identified computationally by searching the genome of ''E. coli'' for intergenic regions of high sequence identity (sequence conservation) with the genomes of closely related bacteria (several salmonella species and ''Klebsiella pneumoniae''). This data was combined with microarray expression analysis and potential novel ncRNAs identified. The expression of novel ncRNA of interest was confirmed by northern blotting. In this large scale screen these ncRNAs were simply referred to as candidates 43, 55 and 61. These 3 ncRNA appear to be highly homologous and are derived from a rep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toxin-antitoxin System
A toxin-antitoxin system is a set of two or more closely linked genes that together encode both a "toxin" protein and a corresponding "antitoxin". Toxin-antitoxin systems are widely distributed in prokaryotes, and organisms often have them in multiple copies. When these systems are contained on plasmids – transferable genetic elements – they ensure that only the daughter cells that inherit the plasmid survive after cell division. If the plasmid is absent in a daughter cell, the unstable antitoxin is degraded and the stable toxic protein kills the new cell; this is known as 'post-segregational killing' (PSK). Toxin-antitoxin systems are typically classified according to how the antitoxin neutralises the toxin. In a type I toxin-antitoxin system, the translation of messenger RNA (mRNA) that encodes the toxin is inhibited by the binding of a small non-coding RNA antitoxin that binds the toxin mRNA. The toxic protein in a type II system is inhibited post-translationally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Membrane Potential
Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. That is, there is a difference in the energy required for electric charges to move from the internal to exterior cellular environments and vice versa, as long as there is no acquisition of kinetic energy or the production of radiation. The concentration gradients of the charges directly determine this energy requirement. For the exterior of the cell, typical values of membrane potential, normally given in units of milli volts and denoted as mV, range from –80 mV to –40 mV. All animal cells are surrounded by a membrane composed of a lipid bilayer with proteins embedded in it. The membrane serves as both an insulator and a diffusion barrier to the movement of ions. Transmembrane proteins, also known as ion transporter or ion pump proteins, actively push ions across the membrane and establish concentration gradi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Translation (biology)
In molecular biology and genetics, translation is the process in which ribosomes in the cytoplasm or endoplasmic reticulum synthesize proteins after the process of transcription (biology), transcription of DNA to RNA in the cell's nucleus (cell), nucleus. The entire process is called gene expression. In translation, mRNA, messenger RNA (mRNA) is decoded in a ribosome, outside the nucleus, to produce a specific amino acid chain, or polypeptide. The polypeptide later protein folding, folds into an Activation energy, active protein and performs its functions in the Cell (biology), cell. The ribosome facilitates decoding by inducing the binding of Base pair, complementary tRNA anticodon sequences to mRNA codons. The tRNAs carry specific amino acids that are chained together into a polypeptide as the mRNA passes through and is "read" by the ribosome. Translation proceeds in three phases: # Initiation: The ribosome assembles around the target mRNA. The first tRNA is attached a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNase III
Ribonuclease III (RNase III or RNase C)(BREND3.1.26.3 is a type of ribonuclease that recognizes dsRNA and cleaves it at specific targeted locations to transform them into mature RNAs. These enzymes are a group of endoribonucleases that are characterized by their ribonuclease domain, which is labelled the RNase III domain. They are ubiquitous compounds in the cell and play a major role in pathways such as RNA precursor synthesis, RNA Silencing, and the ''pnp'' autoregulatory mechanism. Types of RNase III The RNase III superfamily is divided into four known classes: 1, 2, 3, and 4. Each class is defined by its domain structure.Liang Y-H, Lavoie M, Comeau M-A, Elela SA, Ji X. Structure of a Eukaryotic RNase III Post-Cleavage Complex Reveals a Double- Ruler Mechanism for Substrate Selection. Molecular cell. 2014;54(3):431-444. doi:10.1016/j.molcel.2014.03.006. Class 1 RNase III *Class 1 RNase III enzymes have a homodimeric structure whose function is to cleave dsRNA into multiple s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein. mRNA is created during the process of Transcription (biology), transcription, where an enzyme (RNA polymerase) converts the gene into primary transcript mRNA (also known as pre-mRNA). This pre-mRNA usually still contains introns, regions that will not go on to code for the final amino acid sequence. These are removed in the process of RNA splicing, leaving only exons, regions that will encode the protein. This exon sequence constitutes mature mRNA. Mature mRNA is then read by the ribosome, and, utilising amino acids carried by transfer RNA (tRNA), the ribosome creates the protein. This process is known as Translation (biology), translation. All of these processes form part of the central dogma of molecular biology, which describes the flow of genet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rapid Amplification Of CDNA Ends
Rapid amplification of cDNA ends (RACE) is a technique used in molecular biology to obtain the full length sequence of an RNA transcript found within a cell. RACE results in the production of a cDNA copy of the RNA sequence of interest, produced through reverse transcription, followed by PCR amplification of the cDNA copies (see RT-PCR). The amplified cDNA copies are then sequenced and, if long enough, should map to a unique genomic region. RACE is commonly followed up by cloning before sequencing of what was originally individual RNA molecules. A more high-throughput alternative which is useful for identification of novel transcript structures, is to sequence the RACE-products by next generation sequencing technologies. Process RACE can provide the sequence of an RNA transcript from a small known sequence within the transcript to the 5' end (5' RACE-PCR) or 3' end (3' RACE-PCR) of the RNA. This technique is sometimes called ''one-sided PCR'' or ''anchored PCR''. The first step ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Membrane
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (the extracellular space). The cell membrane consists of a lipid bilayer, made up of two layers of phospholipids with cholesterols (a lipid component) interspersed between them, maintaining appropriate membrane fluidity at various temperatures. The membrane also contains membrane proteins, including integral proteins that span the membrane and serve as membrane transporters, and peripheral proteins that loosely attach to the outer (peripheral) side of the cell membrane, acting as enzymes to facilitate interaction with the cell's environment. Glycolipids embedded in the outer lipid layer serve a similar purpose. The cell membrane controls the movement of substances in and out of cells and organelles, being selectively permeable to ions a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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