Anomalous DnaA protein binding to the regulatory region of the Escherichiacoli aldA gene

A binding site for DnaA protein was identified in the regulatory region of the aIdA gene of Escherichia coil. Specific binding was demonstrated by in vitro assays including filter binding as well as mobility shift in a polyac rylamide gel of the DnaA-DNA complex. In cells growing in minimal medium co ntaining glucose, expression of beta -galactosidase activity from an aIdA-I acZ fusion gene was suppressed by oversupply of DnaA protein and was enhanc ed by reducing the free DnaA level. These results suggest that DnaA protein negatively regulates expression of the aIdA gene under these conditions. D espite fairly strong binding, the bound DNA fragment had no consensus 9 bp DnaA binding sequence (DnaA box), and anomalous binding to an AT-rich seque nce located close to the transcription start site was revealed by a footpri nting experiment.