| AVRR | antiviral repressor regulator |
|---|---|
| HCR | heme-controlled repressor; host-cell reactivation; hysterical conversion reaction |
| LAC | La Crosse [virus]; lactase; left atrial circumflex [artery]; left atrial contraction; linguoaxiocerv... |
| LaC | labiocervical |
| lac | laceration; lactation |
| DtxR | Diphtheria toxin repressor |
|---|---|
| ICER | Inducible cAMP early repressor |
| PurR | Purine repressor |
| RAP1 | Repressor Activator Protein 1 |
| Tet R | Tet repressor |
| seed-lac | A species of lac. See the Note under Lac. Source: Websters Dictionary (01 Mar 1998) |
|---|---|
| lac | A resinous substance produced mainly on the banyan tree, but to some extent on other trees, by the Coccus lacca, a scale-shaped insect, the female of which fixes herself on the bark, and exudes from the margin of her body this resinous substance. Stick-lac is the substance in its natural state, incrusting small twigs. When broken off, and the colouring matter partly removed, the granular residuum is called seed-lac. When melted, and reduced to a thin crust, it is called shell-lac or shellac. Lac is an important ingredient in sealing wax, dyes, varnishes, and lacquers. Ceylon lac, a resinous exudation of the tree Croton lacciferum, resembling lac. Lac dye, a scarlet dye obtained from stick-lac. Lac lake, the colouring matter of lac dye when precipitated from its solutions by alum. Mexican lac, an exudation of the tree Croton Draco. Origin: Per. Lak; akin to Skr. Laksha: cf. F. Lague, It. & NL. Lacca. Cf. Lake a colour, Lacquer, Litmus. Source: Websters Dictionary (01 Mar 1998) |
| Lac operon | Group of adjacent and coordinately controlled genes concerned with the metabolism of lactose in E. Coli. The lac operon was the first example of a group of genes under the control of an operator region to which a lactose repressor binds. When the bacteria are transferred to lactose containing medium, allolactose (which forms by transglycosylation when lactose is present in the cell) binds to the repressor, inhibits the binding of the repressor to the operator and allows transcription of mRNA for enzymes involved in galactose metabolism and transport across the membrane (_ galactosidase, galactoside permease and thiogalactoside transacetylase). (18 Nov 1997) |
| lac sulfuris | Sublimed sulfur boiled with lime water, the lime being removed from the precipitate by washing with diluted hydrochloric acid; used in preparing sulfur ointment and in the treatment of various skin disorders. Synonym: lac sulfuris, milk of sulfur. (05 Mar 2000) |
| lac vaccinum | Cow's milk. (05 Mar 2000) |
| active repressor | A repressor that combines directly with an operator gene to repress the operator and its structural genes, thus repressing protein synthesis; active repressor may be repressed by an inducer, with resulting protein synthesis; a homeostatic mechanism for regulation of inducible enzyme systems. (05 Mar 2000) |
| repressor | A type of protein molecule that binds to DNA that shuts up transcription of a gene. See: operon or operator. (09 Oct 1997) |
| repressor gene | A gene that prevents a nonallele from being transcribed. (05 Mar 2000) |
| repressor protein | <molecular biology> A protein that binds to an operator of a gene preventing the transcription of the gene. The binding affinity of repressors for the operator may be affected by other molecules. Inducers bind to repressors and decrease their binding to the operator, while co repressors increase the binding. The paradigm of repressor proteins is the lactose repressor protein that acts on the lac operon and for which the inducers are _ galactosides such as lactose, it is a polypeptide of 360 amino acids that is active as a tetramer. Other examples are the lambda repressor protein of lambda bacteriophage that prevents the transcription of the genes required for the lytic cycle leading to lysogeny and the cro protein, also of lambda, which represses the transcription of the lambda repressor protein establishing the lytic cycle. Both of these are active as dimers and have a common structural feature the helix turn helix motif that is thought to bind to DNA with the helices fitting into adjacent major grooves. (18 Nov 1997) |
| repressor proteins | Proteins which are normally bound to the operator locus of an operon, thereby preventing transcription of the structural genes. In enzyme induction, the substrate of the inducible enzyme binds to the repressor protein, causing its release from the operator and freeing the structural genes for transcription. In enzyme repression, the end product of the enzyme sequence binds to the free repressor protein, the resulting complex then binds to the operator and prevents transcription of the structural genes. (12 Dec 1998) |
| met repressor operator complex | Repressor protein, 104 residues, product of the metJ gene, which regulates methionine biosynthesis in E. Coli. Dimeric molecules bind to adjacent sites 8 base pairs apart on the DNA, sequence recognition is by interaction between antiparallel strands of protein and the major groove of the B form DNA duplex. (18 Nov 1997) |
| inactive repressor | A repressor that cannot combine with an operator gene until it has combined with a corepressor (usually a product of a protein pathway); after activation, the repressor arrests production of the proteins controlled by the operator gene; a homeostatic mechanism for regulation of repressible enzyme systems. Synonym: aporepressor. (05 Mar 2000) |
| translational repressor | A molecule that blocks translation by binding to a messenger RNA. (09 Oct 1997) |
| lactose repressor | Protein (tetramer of 37 kD subunits) that normally binds with very high affinity to the operator region of the lactose operon and inhibits transcription of the downstream genes by blocking access of the polymerase to the promoter region. When the lactose repressor binds allolactose, its binding to the operator is reduced and the gene set is derepressed. (18 Nov 1997) |
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