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Microbiology. 1997 Jun;143 ( Pt 6):2085-95.

The aldA gene of Escherichia coli is under the control of at least three transcriptional regulators.

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Department of Biochemistry, Faculty of Pharmacy, University of Barcelona, Spain.


Expression studies on the aldA gene encoding aldehyde dehydrogenase in Escherichia coli showed induction by two types of molecule (hydroxyaldehydes and 2-oxoglutarate), carbon catabolite repression and respiration dependence. Promoter deletion analysis showed that the proximal operator, which includes inducer-regulator complex and catabolite repression protein (Crp) recognition sites, was necessary for induction by either type of inducer, and that full induction by aldehydes required the cooperation of distal operator sequences beyond position -119. Interactions of the regulator protein with the -59 to -6 fragment were shown by DNA mobility shift assays. Fusions of different deletions of the aldA promoter to lacZ indicated that a Crp site proximal to the transcriptional start point (tsp) was functional in the cAMP-dependent catabolite repression of this system, whereas a distal control site was likely to operate in a cAMP-independent catabolite repression. DNA mobility shift and footprint analyses showed that only the tsp proximal site was bound by pure Crp with a Kd of 5.4 x 10(-7) M. As shown by an Arc-defective strain, the aldA gene seems to be repressed by the Arc system under anaerobiosis, displaying its physiological full induction and activity in the presence of oxygen.

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