|
HslU
The heat shock proteins HslV and HslU (HslVU complex; also known as ClpQ and ClpY respectively, or ClpQY) are expressed in many bacteria such as ''E. coli'' in response to cell stress.Ramachandran R, Hartmann C, Song HK, Huber R, Bochtler M. (2002). Functional interactions of HslV (ClpQ) with the ATPase HslU (ClpY). ''Proc Natl Acad Sci USA'' 99(11):7396-401. The hslV protein is a protease and the hslU protein is an ATPase; the two form a symmetric assembly of four stacked rings, consisting of an hslV dodecamer bound to an hslU hexamer, with a central pore in which the protease and ATPase active sites reside. The hslV protein degrades unneeded or damaged proteins only when in complex with the hslU protein in the ATP-bound state. HslV is thought to resemble the hypothetical ancestor of the proteasome, a large protein complex specialized for regulated degradation of unneeded proteins in eukaryotes, many archaea, and a few bacteria. HslV bears high similarity to core subunits of pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proteasome
Proteasomes are protein complexes which degrade unneeded or damaged proteins by proteolysis, a chemical reaction that breaks peptide bonds. Enzymes that help such reactions are called proteases. Proteasomes are part of a major mechanism by which cells regulate the concentration of particular proteins and degrade misfolded proteins. Proteins are tagged for degradation with a small protein called ubiquitin. The tagging reaction is catalyzed by enzymes called ubiquitin ligases. Once a protein is tagged with a single ubiquitin molecule, this is a signal to other ligases to attach additional ubiquitin molecules. The result is a ''polyubiquitin chain'' that is bound by the proteasome, allowing it to degrade the tagged protein. The degradation process yields peptides of about seven to eight amino acids long, which can then be further degraded into shorter amino acid sequences and used in synthesizing new proteins. Proteasomes are found inside all eukaryotes and archaea, and in so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Shock Protein
Heat shock proteins (HSP) are a family of proteins produced by cells in response to exposure to stressful conditions. They were first described in relation to heat shock, but are now known to also be expressed during other stresses including exposure to cold, UV light and during wound healing or tissue remodeling. Many members of this group perform chaperone functions by stabilizing new proteins to ensure correct folding or by helping to refold proteins that were damaged by the cell stress. This increase in expression is transcriptionally regulated. The dramatic upregulation of the heat shock proteins is a key part of the heat shock response and is induced primarily by heat shock factor (HSF). HSPs are found in virtually all living organisms, from bacteria to humans. Heat-shock proteins are named according to their molecular weight. For example, HSP60, Hsp60, Hsp70 and Hsp90 (the most widely studied HSPs) refer to families of heat shock proteins on the order of 60, 70 and 90 ato ... [...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] |
Covalent
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full valence shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonding is much more common than ionic bonding. Covalent bonding also includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, three-center two-electron bonds and three-center four-electron bonds. The term ''covalent bond'' dates from 1939. The prefix ''co-'' means ''jointly, associated in action, partnered to a lesser degree, '' etc.; thus a "co-valent bond", in essence, means that the atoms share " valence", such a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme Inhibitor
An enzyme inhibitor is a molecule that binds to an enzyme and blocks its activity. Enzymes are proteins that speed up chemical reactions necessary for life, in which substrate molecules are converted into products. An enzyme facilitates a specific chemical reaction by binding the substrate to its active site, a specialized area on the enzyme that accelerates the most difficult step of the reaction. An enzyme inhibitor stops ("inhibits") this process, either by binding to the enzyme's active site (thus preventing the substrate itself from binding) or by binding to another site on the enzyme such that the enzyme's catalysis of the reaction is blocked. Enzyme inhibitors may bind reversibly or irreversibly. Irreversible inhibitors form a chemical bond with the enzyme such that the enzyme is inhibited until the chemical bond is broken. By contrast, reversible inhibitors bind non-covalently and may spontaneously leave the enzyme, allowing the enzyme to resume its function. Reve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Threonine
Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), a carboxyl group (which is in the deprotonated −COO− form under biological conditions), and a side chain containing a hydroxyl group, making it a polar, uncharged amino acid. It is essential in humans, meaning the body cannot synthesize it: it must be obtained from the diet. Threonine is synthesized from aspartate in bacteria such as ''E. coli''. It is encoded by all the codons starting AC (ACU, ACC, ACA, and ACG). Threonine sidechains are often hydrogen bonded; the most common small motifs formed are based on interactions with serine: ST turns, ST motifs (often at the beginning of alpha helices) and ST staples (usually at the middle of alpha helices). Modifications The threonine residue is susceptible to numerous posttranslational modifications. The hydroxyl side-chain can unde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proteolysis
Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called proteases, but may also occur by intra-molecular digestion. Proteolysis in organisms serves many purposes; for example, digestive enzymes break down proteins in food to provide amino acids for the organism, while proteolytic processing of a polypeptide chain after its synthesis may be necessary for the production of an active protein. It is also important in the regulation of some physiological and cellular processes including apoptosis, as well as preventing the accumulation of unwanted or misfolded proteins in cells. Consequently, abnormality in the regulation of proteolysis can cause disease. Proteolysis can also be used as an analytical tool for studying proteins in the laboratory, and it may also be used in industry, for example in food proc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C-terminus
The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is translated from messenger RNA, it is created from N-terminus to C-terminus. The convention for writing peptide sequences is to put the C-terminal end on the right and write the sequence from N- to C-terminus. Chemistry Each amino acid has a carboxyl group and an amine group. Amino acids link to one another to form a chain by a dehydration reaction which joins the amine group of one amino acid to the carboxyl group of the next. Thus polypeptide chains have an end with an unbound carboxyl group, the C-terminus, and an end with an unbound amine group, the N-terminus. Proteins are naturally synthesized starting from the N-terminus and ending at the C-terminus. Function C-terminal retention signals While the N-terminus of a protein often c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Native State
In biochemistry, the native state of a protein or nucleic acid is its properly folded and/or assembled form, which is operative and functional. The native state of a biomolecule may possess all four levels of biomolecular structure, with the secondary through quaternary structure being formed from weak interactions along the covalently-bonded backbone. This is in contrast to the denatured state, in which these weak interactions are disrupted, leading to the loss of these forms of structure and retaining only the biomolecule's primary structure. Biochemistry Proteins While all protein molecules begin as simple unbranched chains of amino acids, once completed they assume highly specific three-dimensional shapes. That ultimate shape, known as tertiary structure, is the folded shape that possesses a minimum of free energy. It is a protein's tertiary, folded structure that makes it capable of performing its biological function. In fact, shape changes in proteins are the primary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Valine
Valine (symbol Val or V) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α- carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a side chain isopropyl group, making it a non-polar aliphatic amino acid. It is essential in humans, meaning the body cannot synthesize it: it must be obtained from the diet. Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, beans and legumes. It is encoded by all codons starting with GU (GUU, GUC, GUA, and GUG). History and etymology Valine was first isolated from casein in 1901 by Hermann Emil Fischer. The name valine comes from valeric acid, which in turn is named after the plant valerian due to the presence of the acid in the roots of the plant. Nomenclature According to IUPAC, carbon atoms forming valine are numbered sequentially s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tyrosine
-Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the Greek ''tyrós'', meaning ''cheese'', as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. It is called tyrosyl when referred to as a functional group or side chain. While tyrosine is generally classified as a Hydrophobe, hydrophobic amino acid, it is more hydrophilic than phenylalanine. It is Genetic code, encoded by the Genetic code#Codons, codons UAC and UAU in messenger RNA. Functions Aside from being a proteinogenic amino acid, tyrosine has a special role by virtue of the phenol functionality. It occurs in proteins that are part of signal transduction processes and functions as a receiver of phosphate groups that are transferred by way of protein kinases. Phosphorylation of the hyd ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycine
Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid (carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinogenic amino acids. It is encoded by all the codons starting with GG (GGU, GGC, GGA, GGG). Glycine is integral to the formation of alpha-helices in secondary protein structure due to its compact form. For the same reason, it is the most abundant amino acid in collagen triple-helices. Glycine is also an inhibitory neurotransmitter – interference with its release within the spinal cord (such as during a ''Clostridium tetani'' infection) can cause spastic paralysis due to uninhibited muscle contraction. It is the only achiral proteinogenic amino acid. It can fit into hydrophilic or hydrophobic environments, due to its minimal side chain of only one hydrogen atom. History and etymology Glycine was discovered in 1820 by the French chemist He ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
