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RNAIII
RNAIII is a stable 514 nt regulatory RNA transcribed by the P3 promoter of the '' Staphylococcus aureus'' quorum-sensing '' agr'' system ). It is the major effector of the ''agr'' regulon, which controls the expression of many '' S. aureus'' genes encoding exoproteins and cell wall associated proteins plus others encoding regulatory proteins The RNAIII transcript also encodes the 26 amino acid δ-haemolysin ( S''taphylococcus aureus'' delta toxin) peptide (Hld). RNAIII contains many stem loops, most of which match the Shine-Dalgarno sequence involved in translation initiation of the regulated genes. Some of these interactions are inhibitory, others stimulatory; among the former is the regulatory protein Rot. In vitro, RNAIII is expressed post exponentially, inhibiting translation of the surface proteins, notably protein A, while stimulating that of the exoproteins, many of which are tissue-degrading enzymes or cytolysins. Among the latter is the important virulence factor, α- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accessory Gene Regulator
Accessory gene regulator (agr) is a complex 5 gene locus that is a global regulator of virulence in '' Staphylococcus aureus''. It encodes a two-component transcriptional quorum-sensing (QS) system activated by an autoinducing, thiolactone-containing cyclic peptide (AIP). Agr occurs in 4 allelic subtypes that have an important role in staphylococcal evolution. The corresponding AIPs are mutually cross-inhibitory, which may enhance the evolutionary separation of the 4 groups. The ''agr'' receptor, AgrC, is a model histidine phosphokinase (HPK) that has been used to decipher the molecular mechanism of signal transduction. AIP binding to the extracellular domain of AgrC causes twisting of the intracellular a-helical domain so as to enable trans-phosphorylation of the active site histidine; the inhibitory AIPs cause the α-helical domain to twist in the opposite direction, preventing trans-phosphorylation. The ''agr'' QS circuit autoactivates transcription of ''agrA'' which, in tur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Staphylococcus Aureus
''Staphylococcus aureus'' is a Gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often positive for catalase and nitrate reduction and is a facultative anaerobe that can grow without the need for oxygen. Although ''S. aureus'' usually acts as a commensal of the human microbiota, it can also become an opportunistic pathogen, being a common cause of skin infections including abscesses, respiratory infections such as sinusitis, and food poisoning. Pathogenic strains often promote infections by producing virulence factors such as potent protein toxins, and the expression of a cell-surface protein that binds and inactivates antibodies. ''S. aureus'' is one of the leading pathogens for deaths associated with antimicrobial resistance and the emergence of antibiotic-resistant strains, such as methicillin-resistant ''S. aureus'' (MRSA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcription (biology)
Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs). mRNA comprises only 1–3% of total RNA samples. Less than 2% of the human genome can be transcribed into mRNA ( Human genome#Coding vs. noncoding DNA), while at least 80% of mammalian genomic DNA can be actively transcribed (in one or more types of cells), with the majority of this 80% considered to be ncRNA. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Transcription proceeds in the following general steps: # RNA polymerase, together with one or more general transcription factors, binds to promoter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Promoter (genetics)
In genetics, a promoter is a sequence of DNA to which proteins bind to initiate transcription of a single RNA transcript from the DNA downstream of the promoter. The RNA transcript may encode a protein (mRNA), or can have a function in and of itself, such as tRNA or rRNA. Promoters are located near the transcription start sites of genes, upstream on the DNA (towards the 5' region of the sense strand). Promoters can be about 100–1000 base pairs long, the sequence of which is highly dependent on the gene and product of transcription, type or class of RNA polymerase recruited to the site, and species of organism. Promoters control gene expression in bacteria and eukaryotes. RNA polymerase must attach to DNA near a gene for transcription to occur. Promoter DNA sequences provide an enzyme binding site. The -10 sequence is TATAAT. -35 sequences are conserved on average, but not in most promoters. Artificial promoters with conserved -10 and -35 elements transcribe more slowly. All D ... [...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 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 for computing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regulon
In molecular genetics, a regulon is a group of genes that are regulated as a unit, generally controlled by the same regulatory gene that expresses a protein acting as a repressor or activator. This terminology is generally, although not exclusively, used in reference to prokaryotes, whose genomes are often organized into operons; the genes contained within a regulon are usually organized into more than one operon at disparate locations on the chromosome. Applied to eukaryotes, the term refers to any group of non-contiguous genes controlled by the same regulatory gene. A modulon is a set of regulons or operons that are collectively regulated in response to changes in overall conditions or stresses, but may be under the control of different or overlapping regulatory molecules. The term stimulon is sometimes used to refer to the set of genes whose expression responds to specific environmental stimuli. Examples Commonly studied regulons in bacteria are those involved in response to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Staphylococcus Aureus Delta Toxin
'Staphylococcus aureus delta toxin is a toxin produced by ''Staphylococcus aureus''. It has a wide spectrum of cytolytic activity. It is among other toxins produced by S. aureus and is part of the phenol-soluble modulin peptide family. Its alpha-helical, amphipathic structure gives it detergent-like properties, allowing it to disrupt and attach to the cytoplasmic membrane of a cell non-specifically, without a receptor, and integrate into the membrane. Delta toxin degrades the membrane on contact and forms short-lived pores, causing cell lysis and subsequent cell death. Structure S. aureus delta toxin is encoded for by the hld gene. The hld gene, of which the 3’ end encodes for delta toxin, is involved in the accessory gene regulator (agr) system. This system controls the signaling and creation of cell-associated and secreted virulence factors. Delta toxin is also secreted from S. aureus without a signal peptide, but the toxin itself has been speculated to make an effective ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shine–Dalgarno Sequence
The Shine–Dalgarno (SD) sequence is a ribosomal binding site in bacterial and archaeal messenger RNA, generally located around 8 bases upstream of the start codon AUG. The RNA sequence helps recruit the ribosome to the messenger RNA (mRNA) to initiate protein synthesis by aligning the ribosome with the start codon. Once recruited, tRNA may add amino acids in sequence as dictated by the codons, moving downstream from the translational start site. The Shine–Dalgarno sequence is common in bacteria, but rarer in archaea. It is also present in some chloroplast and mitochondrial transcripts. The six-base consensus sequence is AGGAGG; in ''Escherichia coli'', for example, the sequence is AGGAGGU, while the shorter dominates in ''E. coli'' virus T4 early genes. The Shine–Dalgarno sequence was proposed by Australian scientists John Shine and Lynn Dalgarno. Recognition Translation start sites Using a method developed by Hunt, Shine and Dalgarno showed that the nucleotide tract a ... [...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] |
Cytolysin
Cytolysin refers to the substance secreted by microorganisms, plants or animals that is specifically toxic to individual cells, in many cases causing their dissolution through lysis. Cytolysins that have a specific action for certain cells are named accordingly. For instance, the cytolysins responsible for the destruction of red blood cells, thereby liberating hemoglobins, are named ''hemolysins'', and so on. Cytolysins may be involved in immunity as well as in venoms. Hemolysin is also used by certain bacteria, such as ''Listeria monocytogenes'', to disrupt the phagosome membrane of macrophages and escape into the cytoplasm of the cell. History and background The term "Cytolysin" or "Cytolytic toxin" was first introduced by Alan Bernheimer to describe membrane damaging toxins ( MDTs) that have cytolytic effects to cells. The first kind of cytolytic toxin discovered have hemolytic effects on erythrocytes of certain sensitive species, such as Human. For this reason "Hemolysin" wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Staphylococcus Aureus Alpha Toxin
Alpha-toxin, also known as alpha-hemolysin (Hla), is the major cytotoxic agent released by bacterium '' Staphylococcus aureus'' and the first identified member of the pore forming beta-barrel toxin family. This toxin consists mostly of beta-sheets (68%) with only about 10% alpha-helices. The ''hly'' gene on the ''S. aureus'' chromosome encodes the 293 residue protein monomer, which forms heptameric units on the cellular membrane to form a complete beta-barrel pore. This structure allows the toxin to perform its major function, development of pores in the cellular membrane, eventually causing cell death. Function Alpha-toxin has been shown to play a role in pathogenesis of disease, as ''hly'' knockout strains show reductions in invasiveness and virulence. The dosage of toxin can result in two different modes of activity. Low concentrations of toxin bind to specific, but unidentified, cell surface receptors and form the heptameric pores. This pore allows the exchange of monovale ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
