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Detyrosination
Detyrosination is a form of posttranslational modification that occurs on alpha-tubulin. It consists of the removal of the C-terminal 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 G ... to expose a glutamate at the newly formed C-terminus. Tubulin polymers, called microtubules, that contain detyrosinated alpha-tubulin are usually referred to as ''Glu-microtubules'' while unmodified polymers are called ''Tyr-microtubules''. The detyrosynating activity was first identified in the late 1970s. It is a slow acting enzyme that uses polymeric tubulin as a substrate. As a result, only stabilized microtubules accumulate this particular modification. Tubulin detyrosination is reversed by the tubulin-tyrosine ligase, which acts only on alpha-tubulin monomer. Since the majority of micr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microtubule
Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 and 15 nm. They are formed by the polymerization of a dimer of two globular proteins, alpha and beta tubulin into protofilaments that can then associate laterally to form a hollow tube, the microtubule. The most common form of a microtubule consists of 13 protofilaments in the tubular arrangement. Microtubules play an important role in a number of cellular processes. They are involved in maintaining the structure of the cell and, together with microfilaments and intermediate filaments, they form the cytoskeleton. They also make up the internal structure of cilia and flagella. They provide platforms for intracellular transport and are involved in a variety of cellular processes, including the movement of secretory vesicles, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Posttranslational Modification
Post-translational modification (PTM) is the covalent and generally enzymatic modification of proteins following protein biosynthesis. This process occurs in the endoplasmic reticulum and the golgi apparatus. Proteins are synthesized by ribosomes translating mRNA into polypeptide chains, which may then undergo PTM to form the mature protein product. PTMs are important components in cell signaling, as for example when prohormones are converted to hormones. Post-translational modifications can occur on the amino acid side chains or at the protein's C- or N- termini. They can extend the chemical repertoire of the 20 standard amino acids by modifying an existing functional group or introducing a new one such as phosphate. Phosphorylation is a highly effective mechanism for regulating the activity of enzymes and is the most common post-translational modification. Many eukaryotic and prokaryotic proteins also have carbohydrate molecules attached to them in a process called gl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tubulin
Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cytoskeleton. Microtubules function in many essential cellular processes, including mitosis. Tubulin-binding drugs kill cancerous cells by inhibiting microtubule dynamics, which are required for DNA segregation and therefore cell division. In eukaryotes, there are six members of the tubulin superfamily, although not all are present in all species.Turk E, Wills AA, Kwon T, Sedzinski J, Wallingford JB, Stearns "Zeta-Tubulin Is a Member of a Conserved Tubulin Module and Is a Component of the Centriolar Basal Foot in Multiciliated Cells"Current Biology (2015) 25:2177-2183. Both α and β tubulins have a mass of around 50 kDa and are thus in a similar range compared to actin (with a mass of ~42 kDa). In contrast, tubulin polymers (microtubules) t ... [...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 ... [...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 hydrophobic amino acid, it is more hydrophilic than phenylalanine. It is encoded by the 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 hydroxyl group can change the activity of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glutamate
Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can synthesize enough for its use. It is also the most abundant excitatory neurotransmitter in the vertebrate nervous system. It serves as the precursor for the synthesis of the inhibitory gamma-aminobutyric acid (GABA) in GABA-ergic neurons. Its molecular formula is . Glutamic acid exists in three optically isomeric forms; the dextrorotatory -form is usually obtained by hydrolysis of gluten or from the waste waters of beet-sugar manufacture or by fermentation.Webster's Third New International Dictionary of the English Language Unabridged, Third Edition, 1971. Its molecular structure could be idealized as HOOC−CH()−()2−COOH, with two carboxyl groups −COOH and one amino group −. However, in the solid state and mildly acidic water solut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyglutamylation
Polyglutamylation is a form of reversible posttranslational modification of glutamate residues seen for example in alpha and beta tubulins Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cytosk ..., nucleosome assembly proteins NAP1 and NAP2. The γ-carboxy group of glutamate may form peptide-like bond with the amino group of a free glutamate whose α- carboxy group can now be extended into a polyglutamate chain. The glutamylation is done by the enzyme glutamylase and removed by deglutamylase. Polyglutamylation of chain length of up to six occurs in certain glutamate residues near the C terminus of most major forms of tubulins. These residues, though themselves not involved in direct binding, cause conformational shifts that regulate binding of microtubule associated proteins (MAP and T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyglycylation
Polyglycylation is a form of posttranslational modification of glutamate residues of the carboxyl-terminal region tubulin in certain microtubules (e.g., axonemal) originally discovered in ''Paramecium '' ''Paramecium'' ( , ; also spelled ''Paramoecium'') is a genus of eukaryotic, unicellular ciliates, commonly studied as a representative of the ciliate group. ''Paramecia'' are widespread in freshwater, brackish, and marine environments and a ...'', and later shown in mammalian neurons as well. See also * Polyglutamylation References {{Protein primary structure Post-translational modification Protein structure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetylation
: In organic chemistry, acetylation is an organic esterification reaction with acetic acid. It introduces an acetyl group into a chemical compound. Such compounds are termed ''acetate esters'' or simply '' acetates''. Deacetylation is the opposite reaction, the removal of an acetyl group from a chemical compound. Organic synthesis Acetate esters and acetamides are generally prepared by acetylations. Acetylations are often used in making C-acetyl bonds in Friedel-Crafts reactions. Carbanions and their equivalents are susceptible to acetylations. Acetylation reagents Many acetylations are achieved using these three reagents: *Acetic anhydride. This reagent is common in the laboratory; its use cogenerates acetic acid. * Acetyl chloride. This reagent is also common in the laboratory, but its use cogenerates hydrogen chloride, which can be undesirable. * Ketene. At one time acetic anhydride was prepared by the reaction of ketene with acetic acid: :H2C=C=O + CH3COOH -> (CH3CO)2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Post-translational Modification
Post-translational modification (PTM) is the covalent and generally enzymatic modification of proteins following protein biosynthesis. This process occurs in the endoplasmic reticulum and the golgi apparatus. Proteins are synthesized by ribosomes translating mRNA into polypeptide chains, which may then undergo PTM to form the mature protein product. PTMs are important components in cell signaling, as for example when prohormones are converted to hormones. Post-translational modifications can occur on the amino acid side chains or at the protein's C- or N- termini. They can extend the chemical repertoire of the 20 standard amino acids by modifying an existing functional group or introducing a new one such as phosphate. Phosphorylation is a highly effective mechanism for regulating the activity of enzymes and is the most common post-translational modification. Many eukaryotic and prokaryotic proteins also have carbohydrate molecules attached to them in a process called gly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
