Activator
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(′ak·tə′vād·ər)
(chemistry) A substance that increases the effectiveness of a rubber vulcanization accelerator; for example, zinc oxide or litharge. A trace quantity of a substance that imparts luminescence to crystals; for example, silver or copper in zinc sulfide or cadmium sulfide pigments.
(genetics) A molecule that modifies a repressor in a way that enables it to stimulate operon transcription.
(graphic arts) accelerator
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activator
IN BRIEF: n. - (biology) any agency bringing about motion..
Young nettles, grass cuttings and comfrey are good natural activators
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Mosby's Dental Dictionary:
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activator
(ak′tivātur)
n
n
1. an alkali, sodium carbonate, which is a component of photographic developing solution that softens and swells the gelatin of the film emulsion and provides the necessary alkaline medium for the developing agents to react with the sensitized silver halide crystals. n 2. a removable orthodontic appliance intended to function as a passive transmitter and sometimes stimulator of the forces of the perioral muscles. One in the myofunctional category of appliances also known by such names as Andresen, Bimler, Monobloc, and Frankel.
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Activator (genetics)
A transcriptional activator is a protein that increases gene transcription of a gene or set of genes.
Most activators are DNA-binding proteins.
Most activators function by binding sequence-specifically to a DNA site located in or near a promoter and making protein-protein interactions with the general transcription machinery (RNA polymerase and general transcription factors), thereby facilitating the binding of the general transcription machinery to the promoter. The DNA site bound by the activator is referred to as an "activator site." The part of the activator that makes protein-protein interactions with the general transcription machinery is referred to as an "activating region." The part of the general transcription machinery that makes protein-protein interactions with the activator is referred to as an "activation target."
Example
The catabolite activator protein (CAP; also known as cAMP receptor protein, CRP) activates transcription at the lac operon of the bacterium Escherichia coli.[1] Cyclic adenosine monophosphate (cAMP) is produced during glucose starvation, binds to CAP, causes a conformational change that allows CAP to bind to a DNA site located adjacent to the lac promoter. CAP then makes a direct protein-protein interaction with RNA polymerase that recruits RNA polymerase to the lac promoter.
See also
- Promoter (biology)
- Repressor
- Operon
- Regulation of gene expression
- Transcription factor
- Glossary of gene expression terms
References
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