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The -arabinose operon, also called the ''ara'' or araBAD operon, is an operon that encodes enzymes needed for the catabolism of arabinose in ''Escherichia coli''. It has both positive and negative regulation and is activated allosterically. It has been a focus for research in molecular biology since 1970, and has been investigated extensively at its genetic, biochemical, physiological, and biophysical levels. In ''E. coli'', arabinose is converted to xylulose 5-phosphate, an intermediate of the pentose phosphate pathway.〔 ==Structure== The structural genes, which encode enzymes for arabinose catabolism, are ''araB'', ''araA'', and ''araD'' (collectively known as ''araBAD''). The regulator gene is ''araC''. The genes ''araBAD'' and ''araC'' are transcribed in opposite directions. * ''araA'' encodes L-arabinose isomerase, which catalyzes isomerization between L-arabinose and L-ribulose. * ''araB'' encodes ribulokinase, which catalyzes phosphorylation of (L/D)-ribulose to form (L/D)-ribulose 5-phosphate. * ''araD'' encodes L-ribulose-5-phosphate 4-epimerase, which catalyzes epimerization between L-ribulose 5-phosphate and D-xylulose 5-phosphate. D-xylulose 5-phosphate and D-ribulose-5-phosphate are metabolites in the pentose phosphate pathway. The operators are ''araI'' and ''araO2''. The operators lie between the ''AraC''. ''AraI'' lies between the structural genes and the operator. The ''araI1'' and ''araI2'' are DNA-binding sites that, when occupied by AraC, induce expression. (Distances not to scale) 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「L-arabinose operon」の詳細全文を読む スポンサード リンク
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