|
LacZ
The ''lactose'' operon (''lac'' operon) is an operon required for the transport and metabolism of lactose in ''E. coli'' and many other enteric bacteria. Although glucose is the preferred carbon source for most bacteria, the ''lac'' operon allows for the effective digestion of lactose when glucose is not available through the activity of beta-galactosidase. Gene regulation of the ''lac'' operon was the first genetic regulatory mechanism to be understood clearly, so it has become a foremost example of prokaryotic gene regulation. It is often discussed in introductory molecular and cellular biology classes for this reason. This lactose metabolism system was used by François Jacob and Jacques Monod to determine how a biological cell knows which enzyme to synthesize. Their work on the ''lac'' operon won them the Nobel Prize in Physiology in 1965. Bacterial operons are polycistronic transcripts that are able to produce multiple proteins from one mRNA transcript. In this case, when lac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lac Operon
The ''lactose'' operon (''lac'' operon) is an operon required for the transport and metabolism of lactose in ''E. coli'' and many other enteric bacteria. Although glucose is the preferred carbon source for most bacteria, the ''lac'' operon allows for the effective digestion of lactose when glucose is not available through the activity of beta-galactosidase. Gene regulation of the ''lac'' operon was the first genetic regulatory mechanism to be understood clearly, so it has become a foremost example of prokaryotic gene regulation. It is often discussed in introductory molecular and cellular biology classes for this reason. This lactose metabolism system was used by François Jacob and Jacques Monod to determine how a biological cell knows which enzyme to synthesize. Their work on the ''lac'' operon won them the Nobel Prize in Physiology in 1965. Bacterial operons are polycistronic transcripts that are able to produce multiple proteins from one mRNA transcript. In this case, when l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta-galactosidase
β-Galactosidase (EC 3.2.1.23, lactase, beta-gal or β-gal; systematic name β-D-galactoside galactohydrolase), is a glycoside hydrolase enzyme that catalyzes hydrolysis of terminal non-reducing β-D-galactose residues in β-D-galactosides. β-Galactosides include carbohydrates containing galactose where the glycosidic bond lies above the galactose molecule. Substrates of different β-galactosidases include ganglioside GM1, lactosylceramides, lactose, and various glycoproteins. Function β-Galactosidase is an exoglycosidase which hydrolyzes the β-glycosidic bond formed between a galactose and its organic moiety. It may also cleave fucosides and arabinosides but with much lower efficiency. It is an essential enzyme in the human body. Deficiencies in the protein can result in galactosialidosis or Morquio B syndrome. In '' E. coli'', the ''lacZ'' gene is the structural gene for β-galactosidase; which is present as part of the inducible system ''lac'' operon which is activ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta-galactosidase
β-Galactosidase (EC 3.2.1.23, lactase, beta-gal or β-gal; systematic name β-D-galactoside galactohydrolase), is a glycoside hydrolase enzyme that catalyzes hydrolysis of terminal non-reducing β-D-galactose residues in β-D-galactosides. β-Galactosides include carbohydrates containing galactose where the glycosidic bond lies above the galactose molecule. Substrates of different β-galactosidases include ganglioside GM1, lactosylceramides, lactose, and various glycoproteins. Function β-Galactosidase is an exoglycosidase which hydrolyzes the β-glycosidic bond formed between a galactose and its organic moiety. It may also cleave fucosides and arabinosides but with much lower efficiency. It is an essential enzyme in the human body. Deficiencies in the protein can result in galactosialidosis or Morquio B syndrome. In '' E. coli'', the ''lacZ'' gene is the structural gene for β-galactosidase; which is present as part of the inducible system ''lac'' operon which is activ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Regulation
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 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 formation of maize seeds, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operon
In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo splicing to create monocistronic mRNAs that are translated separately, i.e. several strands of mRNA that each encode a single gene product. The result of this is that the genes contained in the operon are either expressed together or not at all. Several genes must be ''co-transcribed'' to define an operon. Originally, operons were thought to exist solely in prokaryotes (which includes organelles like plastids that are derived from bacteria), but since the discovery of the first operons in eukaryotes in the early 1990s, more evidence has arisen to suggest they are more common than previously assumed. In general, expression of prokaryotic operons leads to the generation of polycistronic mRNAs, while eukaryotic operons lead to monocistronic mRNA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lac Repressor
The ''lac'' repressor (LacI) is a DNA-binding protein that inhibits the expression of genes coding for proteins involved in the metabolism of lactose in bacteria. These genes are repressed when lactose is not available to the cell, ensuring that the bacterium only invests energy in the production of machinery necessary for uptake and utilization of lactose when lactose is present. When lactose becomes available, it is firstly converted into allolactose by β-Galactosidase (lacZ) in bacteria. The DNA binding ability of lac repressor bound with allolactose is inhibited due to allosteric regulation, thereby genes coding for proteins involved in lactose uptake and utilization can be expressed. Function The ''lac'' repressor (LacI) operates by a helix-turn-helix motif in its DNA-binding domain, binding base-specifically to the major groove of the operator region of the ''lac'' operon, with base contacts also made by residues of symmetry-related alpha helices, the "hinge" heli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Regulation
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 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 formation of maize seeds, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catabolite Activator Protein
Catabolite activator protein (CAP; also known as cAMP receptor protein, CRP) is a trans-acting transcriptional activator that exists as a homodimer in solution. Each subunit of CAP is composed of a ligand-binding domain at the N-terminus (CAPN, residues 1–138) and a DNA-binding domain at the C-terminus (DBD, residues 139–209). Two cAMP (cyclic AMP) molecules bind dimeric CAP with negative cooperativity. Cyclic AMP functions as an allosteric effector by increasing CAP's affinity for DNA. CAP binds a DNA region upstream from the DNA binding site of RNA Polymerase. CAP activates transcription through protein-protein interactions with the α-subunit of RNA Polymerase. This protein-protein interaction is responsible for (i) catalyzing the formation of the RNAP-promoter closed complex; and (ii) isomerization of the RNAP-promoter complex to the open conformation. CAP's interaction with RNA polymerase causes bending of the DNA near the transcription start site, thus effectively catal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lac Operon1
Lac is the resinous secretion of a number of species of lac insects, of which the most commonly cultivated is ''Kerria lacca''. Cultivation begins when a farmer gets a stick that contains eggs ready to hatch and ties it to the tree to be infested. Thousands of lac insects colonize the branches of the host trees and secrete the resinous pigment. The coated branches of the host trees are cut and harvested as sticklac. The harvested sticklac is crushed and sieved to remove impurities. The sieved material is then repeatedly washed to remove insect parts and other material. The resulting product is known as seedlac. The prefix ''seed'' refers to its pellet shape. Seedlac, which still contains 3–5% impurity, is processed into shellac by heat treatment or solvent extraction. The leading producer of lac is Jharkhand, followed by the Chhattisgarh, West Bengal, and Maharashtra states of India. Lac production is also found in Bangladesh, Myanmar, Thailand, Laos, Vietnam, parts of Chi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sugar
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double sugars, are molecules made of two bonded monosaccharides; common examples are sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (two molecules of glucose). White sugar is a refined form of sucrose. In the body, compound sugars are hydrolysed into simple sugars. Longer chains of monosaccharides (>2) are not regarded as sugars, and are called oligosaccharides or polysaccharides. Starch is a glucose polymer found in plants, the most abundant source of energy in human food. Some other chemical substances, such as glycerol and sugar alcohols, may have a sweet taste, but are not classified as sugar. Sugars are found in the tissues of most plants. Honey and fruits are abundant natural sources of simple sugars. Suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galactoside Acetyltransferase
A galactoside is a glycoside containing galactose. The H of the OH group on carbon-1 of galactose is replaced by an organic moiety. Depending on whether the glycosidic bond lies "above" or "below" the plane of the galactose molecule, galactosides are classified as α-galactosides or β-galactosides. A β-galactoside is a type of galactoside in which the glycosidic bond lies above the plane of the galactose Galactose (, '' galacto-'' + ''-ose'', "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose. It is an aldohexose and a C-4 epimer of glucose. A galactose molecu ... residue. The most commonly recognized and used β-galactoside in biochemistry is lactose. However, other chemicals, such as ONPG, are known, but these are typically synthesized for biochemical assays. Galactosides play significant roles in metabolic processes of many organisms and are hydrolyzed by a class of enzymes called g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cellular Transport
A membrane transport protein (or simply transporter) is a membrane protein involved in the movement of ions, small molecules, and macromolecules, such as another protein, across a biological membrane. Transport proteins are integral transmembrane proteins; that is they exist permanently within and span the membrane across which they transport substances. The proteins may assist in the movement of substances by facilitated diffusion or active transport. The two main types of proteins involved in such transport are broadly categorized as either ''channels'' or ''carriers''. The solute carriers and atypical SLCs are secondary active or facilitative transporters in humans. Collectively membrane transporters and channels are known as the transportome. Transportomes govern cellular influx and efflux of not only ions and nutrients but drugs as well. Difference between channels and carriers A carrier is not open simultaneously to both the extracellular and intracellular environments. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
