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The L-arabinose operon of the model bacterium Escherichia coli has been a focus for research in molecular biology for over 40 years, and has been investigated extensively at the genetic, biochemical, physiological, and biophysical levels. It is controlled by a dual positive and negative system. There are 3 structural genes: araB, araA, and araD. They encode the metabolic enzymes for breaking down the monosaccharide sugar arabinose into D-xylulose-5-phosphate, which is then metabolised via the pentose phosphate pathway. The initiator region, containing an operator site as well as a promoter, is called araI (the last letter of araI is an uppercase letter " i "). Near this site lies the araC gene, which encodes an activator protein. The AraC protein binds to initiator region araI.
Additional recommended knowledge
If arabinose is present, it builds a complex: AraC + arabinose
If arabinose is absent, the AraC protein assumes a different conformation. In this conformation the AraC protein binds as well to araI as to ara0 region. Now the DNA is forming a loop. This prevents transcription of the ara operon.
Sequence of the Operon:
araC : araO : araI : araB : araA : araD
(December 2000) "Regulation of the L-arabinose operon of Escherichia coli". Trends in Genetics 16 (12): 559-565.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "L-arabinose_operon". A list of authors is available in Wikipedia.|