期刊
JOURNAL OF BACTERIOLOGY
卷 189, 期 24, 页码 8828-8834出版社
AMER SOC MICROBIOLOGY
DOI: 10.1128/JB.01342-07
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In the oligotrophic freshwater bacterium Caulobacter crescentus, D-xylose induces expression of over 50 genes, including the xyl operon, which encodes key enzymes for xylose metabolism. The promoter (P-xylX) controlling expression of the xyl operon is widely used as a tool for inducible heterologous gene expression in C. crescentus. We show here that P-xylX and at least one other promoter in the xylose regulon are controlled by the CC3065 (xylR) gene product, a LacI-type repressor. Electrophoretic gel mobility shift assays showed that operator binding by XylR is greatly reduced in the presence of D-xylose. The data support the hypothesis that there is a simple regulatory mechanism in which XylR obstructs xylose-inducible promoters in the absence of the sugar; the repressor is induced to release DNA upon binding D-xylose, thereby freeing the promoter for productive interaction with RNA polymerase. XylR also has an effect on glucose metabolism, as xylR mutants exhibit reduced expression of the Entner-Doudoroff operon and their ability to utilize glucose as a sole carbon and energy source is compromised.
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