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PyrG Leader
In molecular biology, the PyrG leader is a ''cis''-regulatory RNA element found at the 5' of the PyrG mRNA. The PyrG gene encodes a CTP synthase, which is involved in pyrimidine biosynthesis. The PyrG leader regulates expression of PyrG, PyrG can form into two different hairpin structures, a terminator or an anti-terminator. Under low CTP conditions, guanine (G) residues are incorporated at a specific site within the PyrG leader, these allow base-pairing with a uracil Uracil () (nucleoside#List of nucleosides and corresponding nucleobases, symbol U or Ura) is one of the four nucleotide bases in the nucleic acid RNA. The others are adenine (A), cytosine (C), and guanine (G). In RNA, uracil binds to adenine via ... (U)-rich region and the formation of an anti-terminator loop, this results in increased expression of PyrG. Under high CTP conditions the guanines are not added, the anti-terminator loop cannot form and instead a terminator loop is formed, preventing further PyrG exp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cis-regulatory Element
''Cis''-regulatory elements (CREs) or ''cis''-regulatory modules (CRMs) are regions of non-coding DNA which regulate the transcription of neighboring genes. CREs are vital components of genetic regulatory networks, which in turn control morphogenesis, the development of anatomy, and other aspects of embryonic development, studied in evolutionary developmental biology. CREs are found in the vicinity of the genes that they regulate. CREs typically regulate gene transcription by binding to transcription factors. A single transcription factor may bind to many CREs, and hence control the expression of many genes ( pleiotropy). The Latin prefix ''cis'' means "on this side", i.e. on the same molecule of DNA as the gene(s) to be transcribed. CRMs are stretches of DNA, usually 100–1000 DNA base pairs in length, where a number of transcription factors can bind and regulate expression of nearby genes and regulate their transcription rates. They are labeled as ''cis'' because they are ... [...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 the ribosome creates the protein utilizing amino acids carried by transfer RNA (tRNA). 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 geneti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CTP Synthase
CTP synthase is an enzyme () involved in pyrimidine biosynthesis that interconverts UTP and CTP. Reaction mechanism CTP (cytidine triphosphate) synthetase catalyzes the last committed step in pyrimidine nucleotide biosynthesis: ATP + UTP + glutamine → ADP + Pi + CTP + glutamate It is the rate-limiting enzyme for the synthesis of cytosine nucleotides from both the ''de novo'' and uridine salvage pathways. The reaction proceeds by the ATP-dependent phosphorylation of UTP on the 4-oxygen atom, making the 4-carbon electrophilic and vulnerable to reaction with ammonia. The source of the amino group in CTP is glutamine, which is hydrolysed in a glutamine amidotransferase domain to produce ammonia. This is then channeled through the interior of the enzyme to the synthetase domain. Here, ammonia reacts with the intermediate 4-phosphoryl UTP. Isozymes Two isozymes with CTP synthase activity exist in humans, encoded by the following genes: * CTPS – CTP synthase 1 * CTPS ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrimidine Biosynthesis
Pyrimidine (; ) is an aromatic, heterocyclic, organic compound similar to pyridine (). One of the three diazines (six-membered heterocyclics with two nitrogen atoms in the ring), it has nitrogen atoms at positions 1 and 3 in the ring. The other diazines are pyrazine (nitrogen atoms at the 1 and 4 positions) and pyridazine (nitrogen atoms at the 1 and 2 positions). In nucleic acids, three types of nucleobases are pyrimidine derivatives: cytosine (C), thymine (T), and uracil (U). Occurrence and history The pyrimidine ring system has wide occurrence in nature as substituted and ring fused compounds and derivatives, including the nucleotides cytosine, thymine and uracil, thiamine (vitamin B1) and alloxan. It is also found in many synthetic compounds such as barbiturates and the HIV drug zidovudine. Although pyrimidine derivatives such as alloxan were known in the early 19th century, a laboratory synthesis of a pyrimidine was not carried out until 1879, when Grimaux reported the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regulation Of Gene Expression
Regulation of gene expression, or gene regulation, includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA). Sophisticated programs of gene expression are widely observed in biology, for example to trigger developmental pathways, respond to environmental stimuli, or adapt to new food sources. Virtually any step of gene expression can be modulated, from Transcriptional regulation, transcriptional initiation, to RNA processing, and to the post-translational modification of a protein. Often, one gene regulator controls another, and so on, in a gene regulatory network. Gene regulation is essential for viruses, prokaryotes and eukaryotes as it increases the versatility and adaptability of an organism by allowing the cell to express protein when needed. Although as early as 1951, Barbara McClintock showed interaction between two genetic loci, Activator (''Ac'') and Dissociator (''Ds''), in the color f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stem-loop
Stem-loops are nucleic acid Biomolecular structure, secondary structural elements which form via intramolecular base pairing in single-stranded DNA or RNA. They are also referred to as hairpins or hairpin loops. A stem-loop occurs when two regions of the same nucleic acid strand, usually Complementarity (molecular biology), complementary in nucleotide sequence, base-pair to form a double helix that ends in a loop of unpaired nucleotides. Stem-loops are most commonly found in RNA, and are a key building block of many RNA biomolecular structure#Secondary structure, secondary structures. Stem-loops can direct RNA folding, protect structural stability for messenger RNA (mRNA), provide recognition sites for RNA-binding protein, RNA binding proteins, and serve as a Substrate (chemistry), substrate for Enzyme catalysis, enzymatic reactions. Formation and stability The formation of a stem-loop is dependent on the stability of the helix and loop regions. The first prerequisite is the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytidine Triphosphate
Cytidine triphosphate (CTP) is a pyrimidine nucleoside triphosphate. CTP, much like ATP, consists of a ribose sugar, and three phosphate groups. The major difference between the two molecules is the base used, which in CTP is cytosine. CTP is a substrate in the synthesis of RNA. CTP is a high-energy molecule similar to ATP, but its role as an energy coupler is limited to a much smaller subset of metabolic reactions. CTP is a coenzyme in metabolic reactions like the synthesis of glycerophospholipids, where it is used for activation and transfer of diacylglycerol and lipid head groups, and glycosylation of proteins. CTP acts as an inhibitor of the enzyme aspartate carbamoyltransferase, which is used in pyrimidine biosynthesis.Blackburn, G. Michael. ''Nucleic Acids in Chemistry and Biology''. The Royal Society of Chemistry, 2006, p. 119-120. See also * CTP synthase * Cytidine * Cytosine Cytosine () (symbol C or Cyt) is one of the four nucleotide bases found in DNA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guanine
Guanine () (symbol G or Gua) is one of the four main nucleotide bases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine ( uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside is called guanosine. With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine- imidazole ring system with conjugated double bonds. This unsaturated arrangement means the bicyclic molecule is planar. Properties Guanine, along with adenine and cytosine, is present in both DNA and RNA, whereas thymine is usually seen only in DNA, and uracil only in RNA. Guanine has multiple tautomeric forms. For the imidazole ring, the proton can reside on either nitrogen. For the pyrimidine ring, the ring N-H can center can reside on either of the ring nitrogens. The latter tautomer does not apply to nucleoside or nucleotide versions of guanine. It binds to cytosine through three hydrogen bonds. In cytosine, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base-pairing
A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA and RNA. Dictated by specific hydrogen bonding patterns, "Watson–Crick" (or "Watson–Crick–Franklin") base pairs (guanine–cytosine and adenine–thymine) allow the DNA helix to maintain a regular helical structure that is subtly dependent on its nucleotide sequence. The Complementarity (molecular biology), complementary nature of this based-paired structure provides a Redundancy (information theory), redundant copy of the genetic information encoded within each strand of DNA. The regular structure and data redundancy provided by the DNA double helix make DNA well suited to the storage of genetic information, while base-pairing between DNA and incoming nucleotides provides the mechanism through which DNA polymerase replicates DNA and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uracil
Uracil () (nucleoside#List of nucleosides and corresponding nucleobases, symbol U or Ura) is one of the four nucleotide bases in the nucleic acid RNA. The others are adenine (A), cytosine (C), and guanine (G). In RNA, uracil binds to adenine via two hydrogen bonds. In DNA, the uracil nucleobase is replaced by thymine (T). Uracil is a demethylated form of thymine. Uracil is a common and naturally occurring pyrimidine derivative. The name "uracil" was coined in 1885 by the German chemist Robert Behrend, who was attempting to synthesize derivatives of uric acid. Originally discovered in 1900 by Alberto Ascoli, it was isolated by hydrolysis of yeast nuclein; it was also found in bovine thymus and spleen, herring sperm, and wheat Cereal germ, germ. It is a planar, unsaturated compound that has the ability to absorb light. Uracil that was formed extraterrestrially has been detected in the Murchison meteorite, in near-Earth asteroid 162173 Ryugu, Ryugu, and possibly on the surface of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
