Catabolite activator protein
- Catabolite activator protein
Catabolite Activator Protein or CAP is a transcriptional activator that exists as a homodimer in solution, with each subunit comprising a ligand-binding domain at the N-terminus (CAPN, residues 1-138), which is also responsible for the dimerization of the protein, and a DNA-binding domain at the C-terminus (DBD, residues 139-209). Two cAMP (cyclic AMP) molecules bind dimeric CAP with negative cooperativity and function as allosteric effectors by increasing the protein's affinity for DNA. Cytosolic cAMP levels rise when the amount of glucose transported into the cell is low, but lactose is readily available.
CAP has a characteristic helix-turn-helix structure which allows it to bind to successive major grooves on DNA. The two helices are reinforcing each causing a 43° turn in the structure so overall causing a 94° degree turn in the DNA. [Schultz SC, Shields GC, Steitz TA (1991).
Crystal structure of a CAP-DNA complex: the DNA is bent by 90 degrees. Science. 253(5023):1001-7. PMID 1653449]
This opens the DNA molecule up, allowing RNA polymerase to bind and transcribe the genes involved in lactose catabolism. CAP thus enhances the expression of the lac operon when lactose is present but not glucose.
This requirement reflects the greater simplicity with which glucose may be metabolized in comparison to lactose. The cell "prefers" glucose, and if it is available, the lac operon is not activated, even when lactose is present.
External links
*}
References
Wikimedia Foundation.
2010.
Look at other dictionaries:
catabolite activator protein — catabolite activator protein. См. белок активатор катаболитных оперонов. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) … Молекулярная биология и генетика. Толковый словарь.
Catabolite Activator Protein — Bei der Katabolitrepression wird die Expression bestimmter Stoffwechselkomponenten (katabolische, also verstoffwechselnde Enzyme) einer Zelle solange unterdrückt, wie ein bestimmtes Stoffwechselprodukt (Katabolit) in signifikanter Menge vorhanden … Deutsch Wikipedia
catabolite activator protein — catabolite gene activator protein CAP; a bacterial protein, activated by cyclic AMP, that stimulates transcription by binding to certain promoter sites on DNA; called also cAMP receptor p. and cyclic adenosine monophosphate receptor p … Medical dictionary
catabolite activator protein — Abbreviation: CAP A protein which combines with cyclic AMP. The cAMP CAP complex binds to the promoter regions of E. coli and stimulates transcription of the relevant operon. Synonyms: catabolite regulator protein (CRP), cyclic AMP receptor… … Glossary of Biotechnology
Activator (genetics) — An activator is a DNA binding protein that regulates one or more genes by increasing the rate of transcription. The activator may increase transcription by virtue of a connected domain which assists in the formation of the RNA polymerase… … Wikipedia
catabolite repression — Inducible enzyme systems in some microorganisms (such as the lac operon) that are repressed when a more favoured carbon source, such as glucose, is available. Repression in E. coli is partially relieved if cAMP is bound to the cAMP catabolite… … Dictionary of molecular biology
Protein — A large molecule composed of one or more chains of amino acids in a specific order determined by the base sequence of nucleotides in the DNA coding for the protein. Proteins are required for the structure, function, and regulation of the body s… … Medical dictionary
activator — 1. A substance that renders another substance, or catalyst, active, or that accelerates a process or reaction. 2. The fragment, produced by chemical cleavage of a proactivator, that induces the enzymic activity of another … Medical dictionary
CAMP receptor protein — Protein Name=PAGENAME caption=Structure of the E. coli Cyclic AMP Receptor Protein. Symbol=CRP AltSymbols=CAP EntrezGene=289905 RefSeq=NP 289905 UniProt=P0ACK0 PDB=1I5Z cAMP receptor protein (in short CRP, also known as catabolite gene activator… … Wikipedia
cAMP receptor protein — catabolite activator p … Medical dictionary
