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Catabolite Activator/Repressor, Cra protein (formerly known as Fructure Repressor FruR) plays a significant role in central carbon metabolism of E coli. Its activity is inhibited by fructose-1,6-bisphosphate (FBP); Cra up-regulate gluconeogeneis pathways and down-regulate glycolysis and carbon-uptake pathways. I found enough literature on how Cra plays a regulatory role in metabolism.

However, I am unable to find out explanation of one experimental observation: with increase in glucose uptake rate the transcript level of cra decreases. What is the mechanism for this. Further, are Cra proteins degraded as the glucose uptake rate increase, if so what is the regulatory mechanism?

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