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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] |
Secondary Structure
Protein secondary structure is the three dimensional conformational isomerism, form of ''local segments'' of proteins. The two most common Protein structure#Secondary structure, secondary structural elements are alpha helix, alpha helices and beta sheets, though beta turns and omega loops occur as well. Secondary structure elements typically spontaneously form as an intermediate before the protein protein folding, folds into its three dimensional protein tertiary structure, tertiary structure. Secondary structure is formally defined by the pattern of hydrogen bonds between the Amine, amino hydrogen and carboxyl oxygen atoms in the peptide backbone chain, backbone. Secondary structure may alternatively be defined based on the regular pattern of backbone Dihedral angle#Dihedral angles of proteins, dihedral angles in a particular region of the Ramachandran plot regardless of whether it has the correct hydrogen bonds. The concept of secondary structure was first introduced by Kaj Ulrik ... [...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] |
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] |
Addiction Module
Addiction modules are toxin-antitoxin systems. Each consists of a pair of genes that specify two components: a stable toxin and an unstable antitoxin that interferes with the lethal action of the toxin. Found first in E. coli on low copy number plasmids, addiction modules are responsible for a process called the postsegregational killing effect. When bacteria lose these plasmid(s) (or other extrachromosomal elements), the cured cells are selectively killed because the unstable antitoxin is degraded faster than the more stable toxin. The term "addiction" is used because the cell depends on the de novo synthesis of the antitoxin for cell survival. Thus, addiction modules are implicated in maintaining the stability of extrachromosomal elements. Proteic Addiction Modules Proteic addiction modules use proteins as toxins and antitoxins, as opposed to RNA or other methods. The known proteic addiction modules all have similar shared characteristics, including placement of the antitoxin ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Death
Cell death is the event of a biological cell ceasing to carry out its functions. This may be the result of the natural process of old cells dying and being replaced by new ones, as in programmed cell death, or may result from factors such as diseases, localized injury, or the death of the organism of which the cells are part. Apoptosis or Type I cell-death, and autophagy or Type II cell-death are both forms of programmed cell death, while necrosis is a non-physiological process that occurs as a result of infection or injury. Programmed cell death Programmed cell death (PCD) is cell death mediated by an intracellular program. PCD is carried out in a regulated process, which usually confers advantage during an organism's life-cycle. For example, the differentiation of fingers and toes in a developing human embryo occurs because cells between the fingers apoptose; the result is that the digits separate. PCD serves fundamental functions during both plant and metazoa (multicellula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Membrane Protein
Membrane proteins are common proteins that are part of, or interact with, biological membranes. Membrane proteins fall into several broad categories depending on their location. Integral membrane proteins are a permanent part of a cell membrane and can either penetrate the membrane (transmembrane) or associate with one or the other side of a membrane ( integral monotopic). Peripheral membrane proteins are transiently associated with the cell membrane. Membrane proteins are common, and medically important—about a third of all human proteins are membrane proteins, and these are targets for more than half of all drugs. Nonetheless, compared to other classes of proteins, determining membrane protein structures remains a challenge in large part due to the difficulty in establishing experimental conditions that can preserve the correct conformation of the protein in isolation from its native environment. Function Membrane proteins perform a variety of functions vital to the sur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasmids
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; however, plasmids are sometimes present in archaea and eukaryotic organisms. In nature, plasmids often carry genes that benefit the survival of the organism and confer selective advantage such as antibiotic resistance. While chromosomes are large and contain all the essential genetic information for living under normal conditions, plasmids are usually very small and contain only additional genes that may be useful in certain situations or conditions. Artificial plasmids are widely used as vectors in molecular cloning, serving to drive the replication of recombinant DNA sequences within host organisms. In the laboratory, plasmids may be introduced into a cell via transformation. Synthetic plasmids are available for procurement over the intern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deletion (genetics)
In genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) (sign: Δ) is a mutation (a genetic aberration) in which a part of a chromosome or a sequence of DNA is left out during DNA replication. Any number of nucleotides can be deleted, from a single base to an entire piece of chromosome. Some chromosomes have fragile spots where breaks occur which result in the deletion of a part of chromosome. The breaks can be induced by heat, viruses, radiations, chemicals. When a chromosome breaks, a part of it is deleted or lost, the missing piece of chromosome is referred to as deletion or a deficiency. For synapsis to occur between a chromosome with a large intercalary deficiency and a normal complete homolog, the unpaired region of the normal homolog must loop out of the linear structure into a deletion or compensation loop. The smallest single base deletion mutations occur by a single base flipping in the template DNA, followed by template DNA strand sli ... [...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] |
Antisense
In molecular biology and genetics, the sense of a nucleic acid molecule, particularly of a strand of DNA or RNA, refers to the nature of the roles of the strand and its complement in specifying a sequence of amino acids. Depending on the context, sense may have slightly different meanings. For example, negative-sense strand of DNA is equivalent to the template strand, whereas the positive-sense strand is the non-template strand whose nucleotide sequence is equivalent to the sequence of the mRNA transcript. DNA sense Because of the complementary nature of base-pairing between nucleic acid polymers, a double-stranded DNA molecule will be composed of two strands with sequences that are reverse complements of each other. To help molecular biologists specifically identify each strand individually, the two strands are usually differentiated as the "sense" strand and the "antisense" strand. An individual strand of DNA is referred to as positive-sense (also positive (+) or simply sense) i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophobic
In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle. Examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar substances from polar compounds. Hydrophobic is often used interchangeably with lipophilic, "fat-loving". However, the two terms are not synonymous. While hydrophobic substances are usually lipophilic, there are exceptions, suc ... [...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] |
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