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P-site
The P-site (for peptidyl) is the second binding site for tRNA in the ribosome. The other two sites are the A-site (aminoacyl), which is the first binding site in the ribosome, and the E-site (exit), the third. During protein translation (biology), translation, the P-site holds the tRNA which is linked to the growing polypeptide chain. When a stop codon is reached, the peptidyl-tRNA bond of the tRNA located in the P-site is cleaved releasing the newly synthesized protein. During the translocation step of the elongation phase, the mRNA is advanced by one codon, coupled to movement of the tRNAs from the ribosomal A to P and P to E sites, catalyzed by elongation factor EF-G. Overview The ribosomal P-site plays a vital role in all phases of translation. Initiation involves recognition of the start codon (AUG) by initiator tRNA in the P-site, elongation involves passage of many elongator tRNAs through the P site, termination involves hydrolysis of the mature polypeptide from tRNA bound to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TRNA
Transfer RNA (abbreviated tRNA and formerly referred to as sRNA, for soluble RNA) is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length (in eukaryotes), that serves as the physical link between the mRNA and the amino acid sequence of proteins. tRNAs genes from Bacteria are typically shorter (mean = 77.6 bp) than tRNAs from Archaea (mean = 83.1 bp) and eukaryotes (mean = 84.7 bp). The mature tRNA follows an opposite pattern with tRNAs from Bacteria being usually longer (median = 77.6 nt) than tRNAs from Archaea (median = 76.8 nt), with eukaryotes exhibiting the shortest mature tRNAs (median = 74.5 nt). Transfer RNA (tRNA) does this by carrying an amino acid to the protein synthesizing machinery of a cell called the ribosome. Complementation of a 3-nucleotide codon in a messenger RNA (mRNA) by a 3-nucleotide anticodon of the tRNA results in protein synthesis based on the mRNA code. As such, tRNAs are a necessary component of translation, the biological ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribosome
Ribosomes ( ) are macromolecular machines, found within all cells, that perform biological protein synthesis (mRNA translation). Ribosomes link amino acids together in the order specified by the codons of messenger RNA (mRNA) molecules to form polypeptide chains. Ribosomes consist of two major components: the small and large ribosomal subunits. Each subunit consists of one or more ribosomal RNA (rRNA) molecules and many ribosomal proteins (RPs or r-proteins). The ribosomes and associated molecules are also known as the ''translational apparatus''. Overview The sequence of DNA that encodes the sequence of the amino acids in a protein is transcribed into a messenger RNA chain. Ribosomes bind to messenger RNAs and use their sequences for determining the correct sequence of amino acids to generate a given protein. Amino acids are selected and carried to the ribosome by transfer RNA (tRNA) molecules, which enter the ribosome and bind to the messenger RNA chain via an anti-c ... [...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] |
A-site
The A-site (A for aminoacyl) of a ribosome is a binding site for charged t-RNA molecules during protein synthesis. One of three such binding sites, the A-site is the first location the t-RNA binds during the protein synthesis process, the other two sites being P-site (peptidyl) and E-site The E-site is the third and final binding site for t-RNA in the ribosome during translation, a part of protein synthesis. The "E" stands for exit, and is accompanied by the P-site (for peptidyl) which is the second binding site, and the A-site ( ... (exit). References Ribosomal RNA {{Genetics-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
E-site
The E-site is the third and final binding site for t-RNA in the ribosome during translation, a part of protein synthesis. The "E" stands for exit, and is accompanied by the P-site (for peptidyl) which is the second binding site, and the A-site (aminoacyl), which is the first binding site. It is involved in cellular processes The cell is the basic structural and functional unit of life forms. Every cell consists of a cytoplasm enclosed within a membrane, and contains many biomolecules such as proteins, DNA and RNA, as well as many small molecules of nutrients and .... Kirillov, S., Makarov, E., & Semenkov, Y. (1983). Quantitative study of interaction of deacylated tRNA with Escherichia coli ribosomes. FEBS Letters, 157(1), 91-94. References * * * Molecular Biology of the Gene, 7th Edition, James D. Watson, Tania A. Baker,Stephen P. Bell,Alexander Gann, Michael Levine,Richard Losick, ©2014 Pearson Ribosomal RNA {{Genetics-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binding Site
In biochemistry and molecular biology, a binding site is a region on a macromolecule such as a protein that binds to another molecule with specificity. The binding partner of the macromolecule is often referred to as a ligand. Ligands may include other proteins (resulting in a protein-protein interaction), enzyme substrates, second messengers, hormones, or allosteric modulators. The binding event is often, but not always, accompanied by a conformational change that alters the protein's function. Binding to protein binding sites is most often reversible (transient and non-covalent), but can also be covalent reversible or irreversible. Function Binding of a ligand to a binding site on protein often triggers a change in conformation in the protein and results in altered cellular function. Hence binding site on protein are critical parts of signal transduction pathways. Types of ligands include neurotransmitters, toxins, neuropeptides, and steroid hormones. Binding sites in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray Crystallography
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their crystallographic disorder, and various other information. Since many materials can form crystals—such as salts, metals, minerals, semiconductors, as well as various inorganic, organic, and biological molecules—X-ray crystallography has been fundamental in the development of many scientific fields. In its first decades of use, this method determined the size of atoms, the lengths and types of chemical bonds, and the atomic-scale differences among various mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lincosamide
Lincosamides are a class of antibiotics, which include lincomycin, clindamycin, and pirlimycin. Structure Lincosamides consist of a pyrrolidine ring linked to a pyranose moiety (methylthio-lincosamide) via an amide bond. Hydrolysis of lincosamides, specifically lincomycin, splits the molecule into its building blocks of the sugar and proline moieties. Both of these derivatives can conversely be recombined into the drug itself or a derivative. Synthesis Biosynthesis of lincosamides occurs through a biphasic pathway, in which propylproline and methylthiolincosamide are independently synthesized immediately before condensation of the two precursor molecules. Condensation of the propylproline carboxyl group with the methylthiolincosamide amine group via an amide bond forms ''N''-demethyllincomycin. ''N''-Demethyllincomycin is subsequently methylated via ''S''-adenosyl methionine to produce lincomycin A. Lincomycin is naturally produced by bacteria species, namely ''Streptomy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macrolide
The Macrolides are a class of natural products that consist of a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. The lactone rings are usually 14-, 15-, or 16-membered. Macrolides belong to the polyketide class of natural products. Some macrolides have antibiotic or antifungal activity and are used as pharmaceutical drugs. Rapamycin is also a macrolide and was originally developed as an antifungal, but is now used as an immunosuppressant drug and is being investigated as a potential longevity therapeutic. Macrolides are bacteriostatic in that they suppress or inhibit bacterial growth rather than killing bacteria completely. Definition In general, any macrocyclic lactone having greater than 8-membered rings are candidates for this class. The macrocycle may contain amino nitrogen, amide nitrogen (but should be differentiated from cyclopeptides), an oxazole ring, or a thiazole ring. Benzene rings are exclude ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleiotropy
Pleiotropy (from Greek , 'more', and , 'way') occurs when one gene influences two or more seemingly unrelated phenotypic traits. Such a gene that exhibits multiple phenotypic expression is called a pleiotropic gene. Mutation in a pleiotropic gene may have an effect on several traits simultaneously, due to the gene coding for a product used by a myriad of cells or different targets that have the same signaling function. Pleiotropy can arise from several distinct but potentially overlapping mechanisms, such as gene pleiotropy, developmental pleiotropy, and selectional pleiotropy. Gene pleiotropy occurs when a gene product interacts with multiple other proteins or catalyzes multiple reactions. Developmental pleiotropy occurs when mutations have multiple effects on the resulting phenotype. Selectional pleiotropy occurs when the resulting phenotype has many effects on fitness (depending on factors such as age and gender). An example of pleiotropy is phenylketonuria, an inherited d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aminoacyl-tRNA
Aminoacyl-tRNA (also aa-tRNA or charged tRNA) is tRNA to which its cognate amino acid is chemically bonded (charged). The aa-tRNA, along with particular elongation factors, deliver the amino acid to the ribosome for incorporation into the polypeptide chain that is being produced during translation. Alone, an amino acid is not the substrate necessary to allow for the formation of peptide bonds within a growing polypeptide chain. Instead, amino acids must be "charged" or aminoacylated with a tRNA to form their respective aa-tRNA. Every amino acid has its own specific aminoacyl-tRNA synthetase, which is utilized to chemically bind to the tRNA that it is specific to, or in other words, "cognate" to. The pairing of a tRNA with its cognate amino acid is crucial, as it ensures that only the particular amino acid matching the anticodon of the tRNA, and in turn matching the codon of the mRNA, is used during protein synthesis. In order to prevent translational errors, in which the wrong ami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cricket Paralysis Virus
Cricket paralysis virus (CrPV) was initially discovered in Australian field crickets ('' Teleogryllus commodus'' and ''Teleogryllus oceanicus'') by Carl Reinganum and his colleagues at the Victorian Plant Research Institute (Burnley, Melbourne, Australia). The paralytic disease spread rapidly through a breeding colony as well as through a laboratory population causing about 95% mortality. This was the first recorded isolate of the virus and is generally referred to as CrPVvic to distinguish it from subsequent isolates. Description The spheroidal, non-enveloped virus particles of CrPV are about 27 nm diameter in negatively-stained electron micrographs and contain a single piece of positive-sense ssRNA. The virion is composed of four capsid proteins with molecular masses generally reported to be 33, 31 and 30 kilodaltons with a minor VP4 protein of about 8 kDa. The particles resemble those of the mammalian picornaviruses but CrPV virions sediment at a faster rate (167 S) th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
